public function getTaxTotal()
    {
        $total = 0;
        $items = $this->Items();
        
        // Calculate total from items in the list
        foreach ($items as $item) {
            $tax = $item->UnitTax;
            $total += $tax * $item->Quantity;
        }
        
        $this->extend("updateTaxTotal", $total);

        $total = MathsHelper::round($total, 2);

        return $total;
    }