src/Model/Order.php
public function calculate()
    {
        if (!$this->IsCart()) {
            return $this->Total;
        }
        $calculator = OrderTotalCalculator::create($this);
        return $this->Total = $calculator->calculate();
    }
public function calculate()
    {
        if (!$this->IsCart()) {
            return $this->Total;
        }
        $calculator = OrderTotalCalculator::create($this);
        return $this->Total = $calculator->calculate();
    }
Calculate the total

@return float the final total