2D Sprites : Texture Atlas Inconsistancy?

[spritakas]

So after examining a sprite sheet that appeared to be sorted, I found that the the width and height actually calculated to:
48.444444444444444444444444444444
49.621621621621621621621621621622
per sprite...
This is a problem, as most practical uses in Texture Atlasing will need an integer, not a floating point/decimal.

How would I go about fixing the sheet properly? I have used gimp but am not familiar with settings snap-to positioning etc. I do not know where to begin to shift sprites by such a marginal amount.

For reference, I am using this sheet:
http://www.sonicgalaxy.net/img/sprites/g...shadow.png
Since the ones hosted on spriter's resource are not setup in this format