Here are the completed words based on your clues:

1. **Change** - you get this back if you pay more for something than it costs
2. **Save** - keep money so that you can buy something with it in the future
3. **Return** - to return something to the place you bought it from
4. **Discount** - a price which is lower than usual
5. **Gift** - give something to someone without asking for payment
6. **Checkout** - the place in a shop where you pay for your goods
7. **Wallet** - you keep your money in this and take it out when you need to
8. **Cost** - the amount of money that you pay to buy something
9. **Receipt** - a piece of paper that proves you have received goods or money
10. **Counter** - the place where transactions take place, often in a shop (this was likely meant as an addition to clue 6 in your list)

Let me know if you need more help!