RateTotal contains a sum of all the tax rates in the document with a matching category and rate.
|Optional rate key is required when grouping.
|If the rate is defined with extensions, they’ll be used to group by also.
|Base amount that the percentage is applied to.
|Percentage of the rate, which may be nil for exempt rates.
|Surcharge applied to the rate.
|Total amount of rate, excluding surcharges