Take a penny, leave a penny
(重定向自Penny tray)

Take a penny, leave a penny (sometimes Give a penny, take a penny, penny tray, or penny pool) refers to a type of tray, dish or cup meant for convenience in cash transactions. They are often found in the United States in gas stations, convenience stores, and other small stores, and were similarly common in Canada before the penny went out of circulation in 2013.