I stopped at the lights in Alicante and a group of young Ecuadorians advanced on the car to clean the windscreen. "No thanks", they did it anyway. So I handed over a mean 50 centimos. One of them put his head through the side window, worried about some sort of snatch and grab I sort of pushed him back. A coin rattled against the inside of the door "I've dropped a euro" he said, the lights were changing, I pulled a euro from my pocket, gave it to him and drove away.
Of course he'd dropped a single centimo to make the right sort of sound as it fell. He made a profit of 99 centimos on that transaction as well as the 50 centimos I'd actually paid.