At the last place I worked, the cafeteria had "penniless" cash registers, always rounding up or down to the nearest nickel. So I got into the habit of dropping silver into one bowl and pennies into another at the end of the day when I emptied my pockets. We were in that building nearly 10 years, during which time I filled a huge cup with pennies.
They moved us to a different building a while back, and the cafeteria here is exact change. I keep a small stash of pennies in my desk at work, and grab a dozen or so pennies from the big cup every couple of days, and always use them at lunchtime. I'm actually bummed when the total comes out to a multiple of five or 10 because I can't get rid of any pennies. But I've worked the big cup down about 10%. It's gonna take a while, but I'm spending those suckers.