> But I've never found a retailer willing to give a $2 bill as change.

Mostly retailers don't stock $2 bills (because they're weird), so if a customer brings a $2, the cashier will put it in their their exceptional bills area, which usually is just large bills. No change is made with exceptional bills, so twos don't get recirculated.

It's hard to even get $10 bills in change these days because of the ways that retailers handle putting larger bills into the safe, and getting smaller bills for change out of the safe.

"Alright. Your total is $25.13. You're paying with $100? No, no, it's fine; I just hope you like fives and ones."