[Wingman4l7]

In the US, IIRC they have a trusted person sort the bills by denomination for them -- like a friend or a bank teller -- and then they fold them into different orientations so they know what they've handed to a checkout clerk. No way for them to prevent being shortchanged, unfortunately.

[HarHarVeryFunny]

I guess technology could help though - this would be a great application for smart glasses.

[IIsi50MHz]

Some countries chose different physical sizes and/or embosed bumps in the corners.