This function will let you round to an arbitrary non-zero number. Zero of course causes a division by zero.
<?php
function roundTo($number, $to){
return round($number/$to, 0)* $to;
}
echo roundTo(87.23, 20); //80
echo roundTo(-87.23, 20); //-80
echo roundTo(87.23, .25); //87.25
echo roundTo(.23, .25); //.25
?>