Having the option to do it either way is good.

Your note at the bottom of: Surcharge Levy Technical Tip says "only one line for each automatic charge will be print on the invoice. If a detail line is required to print or each of the items with surcharges, use items instead".

There's no point having one line that is a combined total print as an item line. Since we're only able to get a combined total using the tax method, it makes sense to put it in the tax section.