ATMs ain’t rocket science.
Learn to count. You know how much her hourly rate is. You know that ATMs only dispense $20s.
So, if her rate is $350 and you get $360 from the cash machine, you know you’re either gonna have to break the $20 before you get there or give her an extra $10.
Don’t go in there all flummoxed about how to make change for a $20. She just gave you a blowjob, don’t ask her to give you change. Don’t ask to take ten minutes off your hour for a ten buck discount. And for fuck’s sake don’t short her $10 off her rate.
If you didn’t get change before you got to the room, suck it up and give her the full amount plus ten. If $10 goddam dollars is gonna make or break your budget, well… jerking off alone is a lot cheaper.