Rounds value up to next quarter integer

round-up-to-quarter.php

<?php

/**
 * Rounds value up to next quarter integer
 * @param  mixed $n
 * @return float
 */
function roundUpToQuarter($n)
{
    if ( ! is_numeric($n)) { return $n; }

    if ($n == 0) { return null; }

    $n  = (float) $n;
    $n *= 1000;
    $x  = 250;

    if ($n % $x !== 0) { $n = round(($n + ($x / 2)) / $x) * $x; }

    $n /= 1000;

    return number_format($n, 2);
}