我在美国，每天都听到这些句子，刚好帮你了，呵呵
1. Do you have XXX card? (xxx 是你所在超市的名字)
Please show your XXX (member) card.
2. Do you need (to buy) a plastic bag?
3. Cash or credit?
4. Please sign here. 或者 May I get your signature here? 或者 Could you please sign here?
5. Three (hundred and) night-eight and fifty cents is your total today.
6. four hundred received
7. one and fifty cents is your change.
8. Here is your receipt.
9. 这个一般这边不说，他们都会说have a good day之类的；不过如果你硬要说的话可以说welcome to visit (us) again.
还有问题M我，Good Luck！