system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Yanks - what on earth is a 'take a penny, leave a penny' jar?
gpt
It is to fill in differences in change when making purchases. Suppose you have $4.25 in change but the purchase costs $4.27; you can just take two pennies from the jar rather than break a larger bill. Alternatively if your purchase was $4.23 you would get two pennies in change, so rather than carry them around you could drop them in the jar for someone else to use.