Unless you plan on paying taxes in all 50 states (you shouldn't), then collecting sales tax from customers outside of the states you are paying taxes in is moot

Unless you plan on paying taxes in all 50 states (you shouldn't), then collecting sales tax from customers outside of the states you are paying taxes in is moot. You generally only need to pay taxes in states you have nexus in (depending on state tax law). In this case, it sounds like you only have nexus in WI which as you mention, does not require sales tax collected. Generally speaking, you are not responsible for sales tax for online sales, outside of the states you are paying taxes in; the customer is. They are supposed to report stuff they bought online and pay their sales tax (ya right...).