Unless a roll is done secretly to avoid revealing information, I prefer to do all my rolling out in the open. Absolutely no fudging. It's more exciting, and it has at least the appearance of impartiality and fairness (though let's be honest, any GM that way inclined can still stack or sway the odds in other ways). As I encourage my players to embrace the highs and lows, the failures and successes, it behooves me to be as fair and impartial as possible and open rolls help visually demonstrate that in part. Yes, a GM could be just as impartial and fudge-free while doing all of their rolls behind the screen, but what then is the point? If nothing else, you loose the very visceral reaction as the players watch that monster's damage roll.
Now, that's not to say you're engaging in badwrongfun if you fudge things; you do what suits you and your group, as long as everyone's onboard with it. But for me and my group, it's a no-no.