When using the Percent column (in the Cost Definitions grid) with the Inventory Tax SKU class type, the percentage applies to SKU items that are designated as "Inventory."
In this example, the 2 inventory items are the Dekton material ($3000) and the sink ($250) which brings the inventory revenue total to $3,250. The 10% inventory tax is $325 which is NOT a part of the pre-tax revenue ($3,500) subject to the state tax. Therefore, the tax total is $614 bringing the revenue total to $4,114.