public function getShippingTax($i = 0, $only = false){
        if (isset($this->itemList[$i]['ShippingTax'])){
            if ($only){
                return $this->itemList[$i]['ShippingTax']['Amount'];
            } else {
                return $this->itemList[$i]['ShippingTax'];
            }
        } else {
            return false;
        }
    }