I leave em on the counter by the cash register in hopes that they'll still be there when some other poor shmoe is thinking how much it sucks to break a bill for that $1.07 soda.
Sometimes I'll toss em in the parking lot, hoping that someone'll pick em up & think they're gonna have good luck. Course, I always feel bad when someone backs over them on account of that penny they're trying to peel off the ground...