As i know you'll need to adjust the product price in cases where the tax rate is 0%. This can be achieved using a combination of catalog price rules, customer groups, and tax classes. Create a customer group for the countries with 0% tax rate (e.g., "Zero Tax Countries"). Create a new tax class for products imported with tax included (e.g., "Imported Products"). Assign the new tax class to the products you import. Create a catalog price rule targeting the "Zero Tax Countries" customer group. In the conditions, specify the countries with 0% tax rate. In the actions of the price rule, set a discount amount that adjusts the price based on your desired calculation (e.g., 15% off for 0% tax rate countries).