I tried that thing today at the petrol station where you try and stop the pump bang on what you want to pay, but let it go a fraction too late and it stopped on £20.03.
"Bollocks!" I shouted and walked into the shop to pay.
"Unlucky, mate," smiled the attendant, who'd seen what I'd done. "Don't worry about the extra."
"Cheers, mate," I said as I handed him my tenner and fucked off.