For anyone who uses this method of calculating sales tax, be aware that Miva is investigating a bug that, in some instances, prevents a customer from checking-out.

Shopper Selected Sales tax is most commonly used when different sales tax rates apply for shipments to certain cities and/or counties. If you don't have to deal with that issue, then this bug should not affect your store. The state-based sales tax calculation seems to work as advertised.

One third-party developer, who has seen this bug in a UK store, believes that it only rears its ugly head if items in the customer's cart have attributes associated with them. Hopefully, Miva will resolve this problem quickly.