public function addTaxAmount(TaxAmount $taxAmount)
    {
        $this->total += $taxAmount->getAmount();

        foreach ($this->taxes as $tax) {
            if ($tax->getTax() == $taxAmount->getTax()) {
                $tax->addAmount($taxAmount->getAmount());
                return;
            }
        }

        $this->taxes[] = $taxAmount;
    }