What do you mean? You should be able to scale up the entire sprite sheet without distortion as long as the scale factor is the same for both axes (X and Y) is a whole number integer.
For example, for a sprite sheet of 128px x 96px, consisting of 4 sprites by 3 sprites, you can scale it up by a factor of 5 to 640px x 480px. This will be a perfect upscale without distortion in Stipple Effect (or in practically any other image editing program, as long as the resize mode is nearest neighbour).