library/Extlib/Utils.php
public function priceBrutto($netto, $tax)
    {
        $tax = round((double) $tax / 100.0, 2);

        if ($tax < 0.00) {
            throw new Exception(sprintf('Tax must be greater than or equal to 0, given %s.', $tax));
        }
        
        if ($tax === 0.00) {
            return $netto;
        }
        
        $result = $netto * ($tax + 1);
        
        return round($result, 2, PHP_ROUND_HALF_UP);       
    }
public function priceBrutto($netto, $tax)
    {
        $tax = round((double) $tax / 100.0, 2);

        if ($tax < 0.00) {
            throw new Exception(sprintf('Tax must be greater than or equal to 0, given %s.', $tax));
        }
        
        if ($tax === 0.00) {
            return $netto;
        }
        
        $result = $netto * ($tax + 1);
        
        return round($result, 2, PHP_ROUND_HALF_UP);       
    }
Count price butto from netto by tax

@param double $netto
@param int $tax
@return double
@throws \Extlib\Exception