Is there a way to add Avalara to a basic Shopify plan?

Hi! I’m curious what happens with tax differences between Shopify Tax and Avalara. We just launched our store and a lot of orders have small but frequent differences between the 2 systems. Usually it’s Shopify charging city and county taxes that Avalara doesn’t. Other times, Shopify uses a county rate and Avalara uses a different county rate. So our accounting team is going crazy over the small but frequent differences in what we the customer is seeing as tax on the invoice generated by Shopify versus the tax we see when we bring it into Avalara?