"He who marches out of step hears another drum." ~ Ken Kesey
Go to the curves, make adjustment layer (Never adjust directly on the file because you can not reverse it if saved) and move the bottom of the curve from 0 to 5.That will make all the dots smaller than 5 to be at least 5%.
UPDATE: OK, this is cool, try it. Open the Curves dialog, we are going to use the "pencil". In the bottom left of the curve box, hover your mouse over the diagonal line, it will tell you what percentage you're on. Click and hold at 5%, drag straight down, and then all the way to the left. All tones 5% and below are gone, and nothing else is affected. Obviously, you can choose any tone as your starting point. I tested with a 0% - 100% grayscale bar in 5% increments, and when I did it, the 5% box just disappeared. Hope this helps...Steve