I mean culturally we're used to it, but it seems really easy to test for and therefore fine businesses doing it in NYC? Just go ring up some purchase and see if they add a tax onto the listed price, and if they do report it.

Agreed, this is totally solvable. You could even set up an email address for people to send pictures of their receipts to so they know who to investigate. Imagine if you could just screenshot a bill and send it to "junkfees@nyc.gov" and then they'd assign someone to look into it!