Nexus for Sales Tax

I plan to use a third party (such as Strike Iron) for sales tax computation.  However, the service wil just return appropriate sales tax for whatever address I provide.

My company only has nexus in 26 states, so we only wish to charge and collect sales tax for those states.

How can I configure nopCommerce to only my third party provider a request for the states desired?

Please share the solution with us here if you know it by now.

Thanks.