Appropriate for "sales" tax scales.
Both the "lookup number" and the "base monetary value" are the sum of the
"taxable net prices" of the OrderItems. (Use the CalculationRule to determine
the TaxCategory.) The "lookup number" is converted to the currency specified
by the currStr attribute of the CalculationScale. The "result multiplier" is
one. The mathematical weights are the "taxable net prices" of the OrderItems.