They actually have something like this in other countries. I can't recall exactly how it works, but it's something like store sells younsomething, you get the receipt, and then it's somehow incentived so that people send their receipts into the government, so people actually do it and then you have a second party that basically reports sales to the government.

No idea. I don't live in the States.

I imagine no one would ever give a receipt for a tip though.