public static BasketItem Calculate( TaxRule taxRule, Basket basket, int shipmentId )
Parameters
- taxRule
 - The tax rule to process
 - basket
 - The basket being processed
 - shipmentId
 - The shipment ID to calculate tax for; pass 0 for unshippable or -1 to ignore shipments
 
Return Value
A basket item for the tax entry, or null if no tax is charged.