I'm horrible at math, so I always 'count up' to make change. For example, if someone is buying something that costs 4.99 and they give me a twenty, I would take the twenty, and then

grab a penny and say "5 dollars"

grab a $5 bill and say "10 dollars"

grab a $10 bill and say "20 dollars"

Works for me every time, and I'm so bad at math, when I hand my students their tests back I warn them to double check their marks! (No, I don't teach math!

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