Yeah, I don't remember the last time I used real coins. I carry a grocery-store branded "quarter" in my car to unlock grocery carts. I use cash to buy coffee, since I buy from a micro-roaster who isn't big enough to bother with accepting plastic, but he prices things so that it's an even $10/lb, so I never have change from that. For just about everything else, I use a credit card (or debit). I pay for our parking meters via cell-phone, and I don't use vending machines (partially due to the fact that I never have change on me). To pay friends for things, I usually just round up or pay with a cheque.
The advantages are having a much lighter wallet. I'm not worried about losing a lot of cash if I ever get mugged, or more likely forget my wallet somewhere. My credit card gives me 1.5% cash back on every purchase I make, plus all the other benefits of using a credit card (warranty, contesting charges, insurance, etc..).
Businesses screw you a lot more than the government. You have to choose your allegiance.. Corporate America or the Government. In this case you have to opt-in to choose the Government.
So you think that money is the root of all evil. Have you ever asked what is the root of money? -- Ayn Rand