What happens if a purchase is $0.02 in Canada?
As someone who works for a company that deploys POS systems in Canada, I can tell you that your best bet would be to have a configuration option that lets the client decide what to do. If they have a business practice that would allow for a sale total to be $0.01 or $0.02, they should first evaluate their business practice.  If you're building a POS system to deploy in Canada, I'm sure you have access to resources (potential clients) who would already know how they would want to handle this. Ask them.