Um, okayyyy... but, uh, you know they have coins in Las Vegas, right? I mean, it's a real city with electricity and banks and restaurants and everything

VERY seriously though - most machines don't even
have coin slots any more. They accept bills and disburse tickets showing your winnings (or, for the more realistic, remaining money). You can then cash in the tickets at machines throughout the casino, or at the Cashier's Cage.
Even there, they only accept two denominations of coins. If you have time, I can find out which two - I think it's quarters & nickels and they won't even accept pennies & dimes.
Really, your best move would be to change the money into bills at home. It'll be easier (lighter) to carry, too!