You can use 2 functions:
- round() - docs here: http://www.php.net/manual/en/function.round.php
- number_format() - docs here: http://ro1.php.net/number_format
I've used both with success, and depending on what you're doing with the result, you may chose either of the above functions.
Later edit: If you want to only round up, you can use ceil() - http://www.php.net/manual/en/function.ceil.php + number format or round
echo round(ceil($number*100)/100,2);
As another user suggested earlier