Everywhere is business casual nowadays for tech (including NYC and Boston). My daughter was even told to wear business casual for an interview at one company so as not to stand out (told by the recruiter). Have him check out the career websites for companies he is interested in - see what the employees are wearing in the pictures and videos - that will give him an idea.
In general only banking is still shirt and tie and even then only in certain areas (probably not in the tech area).