We use Avalara avatax in netsuite as well as in our webstore on the bigcommerce platform. The customer orders their product; tax is calculated using avatax; customer pays. Order is them imported into netsuite with script. All orders that have sales tax and a discount are off by a penny. It used to be more because we used item groups in netsuite but I changed those to kits/packages so the price was independent of the components. I have spoken to Netsuite who says it's avalara issue, Avalara said its netsuite in how they calculate tax,