Can you add a custom TaxCategory on a per item basis to a Sale inline with the Sale POST? Or can you force the sale to not do a tax calculation against the Sale on create?
I'd imagine it'd be a two step process for the first scenario. Step one would involve creating the new custom TaxCategory, and then step two would involve creating a new sale, referencing this new custom TaxCategory.
The second scenario would be pretty simple, if you are talking about flagging a sale as tax free. Create a new tax element as 0% and reference it by its ID when creating a new sale.
Then you have to wait 10 seconds between POSTS though?
Yep. So with scenario #1 that means 20 seconds per transaction if it's a two-step process. POST'ing the new tax element and then POST'ing the new sale referencing the new tax element.