R12 TCA - population of Georgraphic Hierarchies to be used for Address Validaiton but not for sales

The R12 Customer is defined within TCA

TCA has a Geographic Hierarchy - for Country = USA, the hierarchy is State->County->City->Postal Code

I can imagine that there will be thousands of combinations of the above hierarchy

Is the best way to populate the hierarchy via a 3rd party like Vertex or Taxware?  Or are there any other alternatives?

We have very few US Sales Taxable transactions.  So licensing Vertex or Taxware for this purpose might not be necessary.

However, we can see the benefits of Receivables Address Validation - so I am not sure if there is a way to achieve this without loading all the sales tax rates.