El Mahdi
Muad'Dib of the Anauroch
I agree with the idea that there is no such thing as cheating for the DM. I'd call it "Creative Adaptation on the Fly", or "Transient Narrative Modification".
But to be serious, I never roll in the open. Not to detract from others fun and enjoyment of the lethality of random results
, I've just never enjoyed it and neither do my players. I've found my imagination is much better at creating drama and memorable narration than strictly using random dice rolls. I'm much better able to establish a certain level of tension, and maintain it, when I tweak the results, and I can raise or lower that level of tension depending on the feel I want for a given situation or encounter.

But to be serious, I never roll in the open. Not to detract from others fun and enjoyment of the lethality of random results
