public function Total($decimal_size = null)
    {
        if ($this->Cost && $this->Tax) {
            $cost = $this->Cost + (($this->Cost / 100) * $this->Tax);
        } else {
            $cost = $this->Cost;
        }
        
        if($decimal_size) {
            $cost = number_format($cost, $decimal_size);
        }
        
        return $cost;
    }