public function getTotalShippingAttribute()
    {
        if (empty($this->shopCalculations)) $this->runCalculations();
        return round($this->shopCalculations->totalShipping, 2);
    }
public function getTotalShippingAttribute()
    {
        if (empty($this->shopCalculations)) $this->runCalculations();
        return round($this->shopCalculations->totalShipping, 2);
    }
Returns total tax of all the items in cart.

@return float