public function getTaxTotal(): int
    {
        $taxTotal = 0;

        foreach ($this->getAdjustments(AdjustmentInterface::TAX_ADJUSTMENT) as $taxAdjustment) {
            $taxTotal += $taxAdjustment->getAmount();
        }

        foreach ($this->units as $unit) {
            $taxTotal += $unit->getTaxTotal();
        }

        return $taxTotal;
    }