VAT total amount SHOULD be the sum of order line tax amounts, if order line tax amounts are provided
/ubl:Order(cac:TaxTotal and (xs:decimal(cac:TaxTotal/cbc:TaxAmount)) = (round(xs:decimal(sum(/ubl:Order/cac:OrderLine/cac:LineItem/cbc:TotalTaxAmount)) * 10 * 10) div 100)) or not(/ubl:Order/cac:OrderLine/cac:LineItem/cbc:TotalTaxAmount)