Change back from my dollar?

I stopped to get gas the other day and the gauge showed the needle to be half way between a quarter tank and the E for "start walking". The price for regular was $3.37 and the way the prices have been rising lately I thought maybe I should bite the bullet and fill the tank, which would last me a little more than two weeks, even with not having the greatest mpg. I figured the tank to be about fifteen gallons and a little quick math told me it would cost in the range of forty dollars. I had already filled up once in the past for thirty four dollars, which for me was unbelievable, so I knew what to expect. I did have a fifty in my wallet, so I pulled it out, told the guy to fill it with regular and that it was a cash purchase. I sat listening to some jazz on WBGO and then heard the click of the nozzle, indicating it was full. I glanced at the pump and it said $49.60. OMG. He squeezed another forty cents in, I handed him my fifty, told him to have a nice day, and drove away. But, OMG. Fifty dollar bill and no change. OMG. I have gotten fifty before, but that was fifty cents worth, back when I first started to drive. I am glad I don't commute to work and now can feel the pain of those that do.