Seeking a better way to force a tax recalculation with eBTax

In our R12 instance, new Suppliers are not defaulting in the Allow Tax ability to checked and it's causing the  Supplier Site Tax details to default in Calculate Tax as No.  This is causing a problem in the Purchase Orders.  The problem isn't noticed until the buyer checks on taxablity after creating the PO.  They usually notice it after it's been approved and before it gets mailed out to the suppler.
The work around we have found is once  the tax the supplier is updated and the PO has to be unreserved (we use Grants).  The quantity must be changed and then changed back to force the eBTax to re-fire and calculate the tax.