Untitled

Given a decimal time value, how could I round that to an interval?
function round_decimal_time($time, $interval=15){
  // Split up decimal time
  $hours = (int) $time;
  $minutes = $time - $hours;

  // Convert base 10 minutes to base 60 minutes
  $b60_m = $minutes * 60;

  // Round base 60 minutes to nearest interval... (15 minutes by default)
  // DONT KNOW HOW TO DO THIS PART

  // If greater than or equal to 60, go up an hour
  if($b60_m >= 60){
      $hours += 1;
      $minutes = 0;
  } else {
    // Otherwise, convert b60 minutes back into b10
    $time = $hours + ($b60_m / 60);
  }

  return $time;
}

Input: 5.66 (5:39 duration)
Output: 5.75

Input: 5.6 (5:36 duration)
Output: 5.50

Input: 5.05 (5:03 duration)
Output: 5.00

round($number/$X)*$X;

round(39.6/15)*15=45

round_decimal_time($time,$round=15){
     return (round($time * 60 / $round) * $round) / 60;
 }

$a = 5.66;
var_dump(round($a / 0.25) * 0.25);

round(7 / 5) * 5