code: public static function MROUND($number, $multiple)
      {
          $number = Functions::flattenSingleValue($number);
          $multiple = Functions::flattenSingleValue($multiple);
  
          if ((is_numeric($number)) && (is_numeric($multiple))) {
              if ($multiple == 0) {
                  return 0;
              }
              if ((self::SIGN($number)) == (self::SIGN($multiple))) {
                  $multiplier = 1 / $multiple;
  
                  return round($number * $multiplier) / $multiplier;
              }
  
              return Functions::NAN();
          }
  
          return Functions::VALUE();
      }
docs: MROUND.
  
  Rounds a number to the nearest multiple of a specified value
  
  @param float $number Number to round
  @param int $multiple Multiple to which you want to round $number
  
  @return float Rounded Number