If you’d return a hundred, return the five. Honesty doesn’t have a minimum order.

Size is the excuse that does the work here. Returning a large sum feels obvious because the amount makes the rule visible, and the same rule applies to the small one with nothing but your own attention to enforce it. The amount only changes what you can get away with telling yourself. A five is also somebody’s lunch.

Next time you find something small, treat the number as irrelevant and ask only whose it is. Hand it in, say where you found it, and skip the calculation entirely. Keeping the threshold at zero saves you from negotiating with yourself every time.