Yo! Yank ... Re: Er ....
Actually its trivial. Really.
I mean the Feds could set up a web service where you enter your zip code and you can get the array / json object of each tax spelled out for you. The onus would then be on the local government to maintain their taxes else either lose out or payout a refund if they repeal a tax and forget to update it.
But SCOTUS didn't go that far. They only went to the State level, which is extremely trivial (50+ data point for states and territories) And you could create a service to assist. Sales tax rates are slow to change.
Again, the truth is that this is rather easy but no one wanted to do it.