money-and-rounding.txt
My app handles money here: <paste>

Check it properly:
- Am I using floats anywhere? Show me where and change it to integer
  minor units or a decimal type.
- Where does rounding happen, and does it happen exactly once?
- Is the currency stored alongside the amount, or assumed?
- Do totals recompute from the parts, or get stored and drift?

Show me a worked example where my current code loses or gains a penny.

Ask for the worked example. A concrete "£19.99 × 3 gives you this" is more persuasive, and more testable, than any explanation of binary fractions.