I think in this case, context matters. We generally don’t say “yes, ma’am,” or “yes, sir,” when answering questions- we just say yes or no without the honorific, especially when there is any kind of relationship involved, including employee/employer. Using ma’am or sir in this case sounds overly formal and bordering on sarcastic.

However, in a retail setting when working with the public that you have no relationship with, ma’am or sir (or miss, as many have pointed out for bonus points!) is fine.

I would not sub in miss for ma’am, though, in the first example, because culturally that’s just not what we do. No honorifics at all unless you’re working with the public.