I admit, I don't always have enough cash on me, and the market has inexpensive, beautiful flowers, fruit in season and really good samosas. So, I'd go into the convenience store and buy something (a bottled water, some milk) and use the ATM to get cash back.
Fast forward to the day before payday. I have about $38 left in my account. I go into the store and see that the sign now says "Cashback Fee $2) Oh, well.
$20 isn't quite enough, and I can't do $40. But when the "Cashback?" prompt comes up, instead of punching in numbers, I can now get increments of $20.
"Can I get $30?" I ask the cashier.
"Is this a new..."
"YOU GET TWENTY! FORTY! SIXTY!"
I took twenty. I now go to the bank, because that ATM doesn't yell at me.