Pay the toll for the next person or next few people in line (done this several times!)

Or at the grocery store if you have to use a quarter to get a cart, don't return it and get your quarter back. (My 5yo dd loves to do this and see the smile on the person's face when they get it.) She also loves when I let people in traffic go ahead of me, can't say I LIKE to do it, but obviously it sets a good example for her.