Martin Fowler's money pattern [0] solves this problem. Just make sure whenever you're dealing with currencies to use a value object for money, rather than float. Lots of languages have libraries for this pattern. [1]
You don't know the history of your craft; study more, look into where agile came from, the extreme programming movement, and who was involved and how refactoring became a thing. Names like Ward Cunningham, Kent Beck, Martin Fowler, Ron Jeffries, Rob Martin, and Dave Thomas should be familiar to anyone who knows their craft.