I didn't mean to imply that fudging rolls was bad, necessarily. However, I always feel a little patronized as a player when I suspect the DM is fudging, so I like to remove all doubt. When I fudge a monster's tactics (a very rare occurrence, by the way), it's far less obvious than a DM rolling behind a screen, announcing 10 misses in a row.
For the few rolls that absolutely must be kept secret, I can hide the roll behind my hand. It doesn't come up that often. Usually, if the players don't even know what the roll is for, there's no need to hide it.