Why do people say "if I had a nickle for every time"?

"If I had a nickle for every time" is a common saying used in the English language to describe a situation that happens repeatedly. The implication, which is meant to be an exaggeration, is that the individual would be wealthy or make substantial money due to the volume of times the event is repeated. Oftentimes, it refers to a question or comment that an individual hears repeatedly.