The TaxPricingEngine component is a preconfigured implementation of the TaxPricingEngineImpl class. It determines the price of tax for an order by invoking a series of TaxPricingCalculators. It uses the same mechanisms as the ItemPricingEngine component for determining which promotions to apply to taxes.

The TaxPricingCalculator determines if an item is taxable using pricingTools.isTaxable() method. If an item is taxable, pricingTools.isTaxable() returns true. By default, all items are taxable. pricingTools.calculateTaxableAmount() then determines the tax by returning 0 if isTaxable returns false, otherwise it returns the price of the item minus its orderDiscountShare.

You can view and modify this component in the ATG Control Center. Its location is /atg/commerce/pricing/TaxPricingEngine.