Found a more flexible way
Add column ProductTaxRate to the product table in the DB
Add Column Taxrate to ecart
get it into the cart - add to cart button binding
Taxrate=<?php echo $row_rs_products['ProductTaxable']; ?>
add Calculation ItemTax = [Price] * [Taxrate]*[Quantity]
then tax calc (currently cant do this as mentioned about - dropdowns don't show added values)
//eCart Rule
function WAEC_eCart1_ItemTaxVal() {
$totalTax = 0;
if (true && (($this->TotalColumn("ItemTax") > 0))) {
$totalTax += ($this->TotalColumn("ItemTax") + 0);//Result
}
return WA_eCart_FormatNumber($totalTax, $this->ForceDecimalsC, $this->DecimalPlacesC);
}
//eCart Rule