Hi John,
It probably depends on how customer focused the shop is. Around here it'll probably go something like this "Right ... that's $20 thanks - will that be cash or EFTPOS?". Actually, I lie ... they probably won't say the "thanks" bit.
Most aren't in a hurry to reprint anything at their expense - especially if they perceive that it's not their fault, and no, they generally don't do themselves any favours with this approach in my opinion.