Common/Calculator/Amount.php
public function addTaxAdjustment(Adjustment $tax): void
    {
        foreach ($this->taxes as $t) {
            if ($t->isSameAs($tax)) {
                $t->addAmount($tax->getAmount());

                return;
            }
        }

        $this->taxes[] = clone $tax;
    }
public function addTaxAdjustment(Adjustment $tax): void
    {
        foreach ($this->taxes as $t) {
            if ($t->isSameAs($tax)) {
                $t->addAmount($tax->getAmount());

                return;
            }
        }

        $this->taxes[] = clone $tax;
    }
Adds the tax adjustment.

@param Adjustment $tax