protected function setPayableAndRoundOff()
    {
        switch (config('cart_manager.round_off_to')) {
            case 0.05:
                // https://stackoverflow.com/a/1592379/3113599
                $this->payable = round($this->total * 2, 1) / 2;
                break;

            case 0.1:
                $this->payable = round($this->total, 1);
                break;

            case 0.5:
                // http://www.kavoir.com/2012/10/php-round-to-the-nearest-0-5-1-0-1-5-2-0-2-5-etc.html
                $this->payable = round($this->total * 2) / 2;
                break;

            case 1:
                $this->payable = round($this->total);
                break;

            default:
                $this->payable = $this->total;
        }

        $this->roundOff = round($this->payable - $this->total, 2);
    }