public function round(): void
    {
        $this->unit = Money::round($this->unit, $this->currency);
        $this->gross = Money::round($this->gross, $this->currency);
        $this->discount = Money::round($this->discount, $this->currency);
        $this->base = Money::round($this->base, $this->currency);
        $this->total = Money::round($this->total, $this->currency);
        $this->tax = Money::round($this->total - $this->base, $this->currency);
    }