My client only collects tax for New Jersey and New York because that's what is permitted by those states for the products they're selling. My only options here are A) include tax with all products and send customers in NJ and NY a separate bill for the tax, or B) tax everyone and send customers outside of NJ and NY a refund for the tax amount.
Both very inefficient and inconvenient options.
I have this problem with Canadian provinces. The other solution I've thought of is like your A) solution, but build a separate page for each province/state, and in the UI they first select country, then province/state (my client sells to Canada and US). Then you list on this product web page what taxes are included in the price, and I believe you could also put a note in the receipt specific to that product. Hopefully groups of states charge the same amount in the end and you don't have to build 50+ pages for one product!