Okay, this little issue involves a bunch of smaller issues.  First and foremost, stuff in vending machines is starting to cost more than a buck.  Second, so little stuff overall costs a buck, that fives are more common.  Most vending machines will not take fives.

YouTube

So why not take a five spot?  Well first off it's a change issue.  If you buy a bucks worth of stuff you're going to get back 16 quarters. That's a lot of metal in your pocket.  So, this takes us to the dollar coin. It's time folks. I don't know what everybody's problem with dollar coins is, but it's time to suck it up.  Not only will they allow larger denominations for vending, they are they cheaper than paper bills in the long run (paper bills can only circulate for so long until they get raggedy and the mint has to replace them).

I like those big gold dollar coins. They make me feel like a pirate.  They're sturdier and you feel like you have money in your pocket because they have a little weight to them.  I also like that they will enable us to use vending machines without it sounding like we're playing a slot machine.