Last night, while in Princes Risborough, I spent the un-princely sum of £1.20 and paid with a £20 note.
After handing over the note, I then realised that I had a 20p coin, so handed that over as well. In my world that is called 'making it easier' for the assistant.
The cash register told the girl serving me to hand me back £18.80. Giving her the extra 20p totally blew her mind and she could then not work out how much change to give me. Duh!