I agree with getting reimbursed for ongoing expenses - if the $10 was just an occasional thing it would be different. If the MIL doesn’t want to add you onto a CC or checking account, maybe keep a tally of the expenses and then just have her reimburse you once a month.
Since you ask…
In this case it was only $10. Your husband waived it off this time. You should have accepted that. It’s not worth all the hassle of tension between you and your spouse. Waiving off the small amount of $10 (cost of lunch at Subway!) doesn’t equate to never accepting reimbursement going forward.
Honestly, I think this is wrong as well:
"Typical situation: When everyone was returning to base for the funeral week, SIL spent $200 to stock up the MIL/FIL house with food for the incoming hoard (it was empty for the season when they winter over in the south). H gave SIL $100 because MONEY. Not sure why it was our responsibility to pay for stocking the house (there are 5 siblings) since we live in the same place and were not the ones eating all that food, but that’s how it is. "
Your FIL just passed away. If it makes your husband feel better and more helpful chipping in $100 for food, so be it. To be concerned about a measly $100 (sounds like you can afford it) at such an emotional time for the family seems a little petty to me (and it does speak to other issues/history IMO).
ETA: I don’t feel to the need to be “equal” with my own parents or in-laws even though both have assets. At this stage in our lives, if my husband and I can treat or pick up the bill once in awhile, we do it. They paid for the first 20+ years of our life and have been generous with different things when we were getting established early in our adult years. They won’t be around forever, so if we can show them our appreciation and respect and we pull out our wallets more than they do now, I’m good with that and glad we can afford to do it.
This:
@doschicos:
“In this case it was only $10. Your husband waived it off this time. You should have accepted that. It’s not worth all the hassle of tension between you and your spouse. Waiving of the small amount of $10 (cost of lunch at Subway) doesn’t equate to never accepting reimbursement going forward.”
Here’s what I think some of you missed:
“Since she has a hard time getting around, one of the things I am trying to do now is pick up things at the market once a week or when I happen to be going I ask if she needs something. I get a separate bill and have them bagged separately and she reimburses me when I take them in.”
This is not a one time $10 charge. She is/will be doing this often, there is an agreement. The husband making a big deal, when this is the agreement between his wife and mother, seems a little much. I understand that people get crazy during times of stress, but it sounds like MIL and wife have it all worked out, so no one has resentment, and nobody has guilt. Seems like a win/win.
I didn’t miss that at all, @busdriver11. The husband waved it off this time - a whopping $10!! - and the OP should have let him and let it be. If it makes him feel better and that he is being “helpful” (lots of men especially, rightly or wrongly, show this through purchases/providing), she should have let it be IMO. Sure is cheaper than marital counseling. 
I think you have to be careful with the money thing. People are funny about that. I have a tendency to always whip out my credit card and pay for everyone, that’s just pure habit. And sometimes it offends people. I have one friend who muttered, “I’m not a child”, so I quickly said why don’t we split it. I used to always pay for other people, even when we were broke (which really aggravated my husband). He still gets aggravated when I pay for others every time. Some times, people will just let you keep paying (and expect you to always pay), making you feel taken advantage of. One person that I used to go out with a lot…when the bill came, she told the waitress to give it to me because I ALWAYS paid. And when she put it like that, it kind of bothered me, especially since we were trying to pay down debt. I guess I wanted her to at least make a pretense at splitting or paying the bill.
There’s often plenty of family history to go along with this issue. I suspect after reading the OP’s first post, that there are disagreements with her and her husband about this already.
So $10 was insignificant, true, but how am I supposed to know where the dividing line is if that was the agreement beforehand? Is it $10, $100, $1000, or what?
FIL used to do this thing - he would say “oh let us give you something for all that food you brought” if he thought we spent more than warranted on Sunday dinner fixings. H would protest and FIL would stuff a $20 into my hands under the counter. I learned not to argue and stuffed any such funds into my pockets. I don’t want to get involved in their ridiculous shenanigans.
I also don’t want to be sending the siblings weekly bills for the groceries or getting weekly invoices from them. I do want to know what the plan is. If we’re going to pay for her stuff that we get, then say so. If there’s a dollar limit, then say so. If we are to assume she’s impoverished, then say so.
Hey, I say if he wants to be helpful, he should get his butt out there and do the shopping and cooking for Mom. Otherwise, he should shuddup about it already! 
I feel there’s a lot more history to this than just ten bucks.
Actually it does, since any likely amount would be small, relatively speaking.
Is your husband going to be there every time and if so, does he plan to wave it off every time? I still think one time doesn’t equate to a pattern. If you are concerned that it will be perceived to be such, then discuss that with your husband once you both calm down.
Personally, if it was just $10 or so a week, I personally wouldn’t worry about it much but that is me. We all bring our own histories and baggage regarding money with us into these situations. My guess is you and your husband grew up in families where money was treated differently. Is this true? Did you grow up in a situation where money was tighter or not as freely spent? It sounds like a much bigger issue than just this one incident. This incident sounds like a symptom of the problem, not the problem itself.
Reimbursement for small amounts does look and feel petty, even when there’s a specific agreement. The best way to handle the situation was suggested by others - use your MIL’s money. Get added to one of her credit cards and use that, or just have her give you fixed amounts like say $500/month and you act like a bank and just deduct from that on a spreadsheet. If the balance grows then tell MIL when she can skip a month.
I would say that if your husband has family/siblings that is weird about money, keep very good records if you get access to accounts or lump sum. People can get really weird about money and if someone ever questions things, its best to have everything above board and recorded. Sometimes money + family = drama.
^ok, it’s still not clear to me what is “small”?
As issues go, for years I’ve been concerned that of the 4 of us (H, myself, BIL, and his wife) if we had to take care of MIL and or FIL, I would be on the front line. Now we are beginning to see how that plays out.
Already, H says “well I can go on Tuesday and make her dinner, etc.” But 3 Tuesdays in a row I have bought food and made dinner. And doing the grocery thing, and starting to chauffeur.
SIL is helping with some things, but she is sick A LOT. H appears in time to eat. I’m ok with this but there is a clear pattern here. This is not easy for me, and it’s hard to know where the lines are. Actually, H doesn’t have any lines, so there’s that.
sorry, double post
I can tell this is about a lot more than just money!
Oh man, I’m not ready to start taking care of people. Let it not happen for a long time!
This is what is really sticking with me. Your MIL just lost her husband. Your husband and his siblings lost their father. People have traveled from out of town, and there is no food in the house. You seem unreasonably irritated that your husband kicked in $100 to make the house more comfortable for MIL and the sibs that were staying there…because you weren’t eating there? Because it wasn’t your responsibility? How is that throwing money around?If it is your hometown and others had to travel, all the more reason for you to be generous. I can’t imagine being concerned over $100 shared with family when my husband and in laws were grieving. I would use the word petty rather than greedy.
@planner03, I’d say that you aren’t seeing the entire picture here. Look at post 32. This is about a lot more than just money. It’s history, expectations, and who is now doing the work. Not just one day.
“@planner03, I’d say that you aren’t seeing the entire picture here. Look at post 32. This is about a lot more than just money. It’s history, expectations, and who is now doing the work. Not just one day.”
Right. So quibbling over whether accepting $10 is greedy isn’t going to fix it.
@sylvan8798 I think you should separate out the $ issue and the “being on the front line” and the pattern of being expected to do things for MIL issue. Both might be important to you and both involve your husband and your interactions with family but they are separate issues IMO. If you are already resenting the weekly pattern and the feeling that the brunt of the responsibility is falling on you rather than your husband or his siblings, you need think about what you want to be responsible for and address that before it festers more. Your post #32 is much different than what you outlined in your original post and speaks to feeling put upon.
@busdriver11 Oh, I saw the full picture. OP chose that particular example and I found it very telling. Funny thing about asking for opinions-not everyone will agree with you! I assume that OP posted because she actually wanted to know how others perceived her attitude, not just to get a pat on the back from those that agree.