the machines can really get full, even with no singles involved. Plenty of slot machines in Bally's and Caesars takeR$1 bills. Just because it's not listed on the machine, doesn't mean that it will not be accepted.
All Slot machines have a bill accepter similar to what is on a vending machine. You walk up put yourR$5R$10R$20R$50 orR$100 into the machine presto you now have credits.