What should I do to reproduce the problem? What page should I start at? What should I add to the cart? What do you expect to happen? What happens instead?
You can add an IF statement to the checkout button to make sure it doesn't show if the cart contents are less than $10. You could also add a redirect from the checkout page to an error page if the cart contents are under $10. Is that what you want to do?
Please provide as much detail as possible about what you are doing and what you want to happen and I can try to help.