It's a JIS screw. You can read about it here. A normal phillips head will strip it because it's not deep at the center. The best way to get those if you don't have a set of JIS drivers is to just use a flathead with care (EDIT: or grind down a phillips head driver a bit flatter.)
A normal screw might work, but I think the issue is that they won't seal well enough to keep from draining.