Force Div to expand in specific intervals

[MythX]

I have a div with a repeating background image. I need this div to grow based on the content within it. The problem is, if the background image is cut off in the middle, it just doesn't line up right with other images. Is there a way to allow the div to expand its length in units of 20px at a time? Preferably I'd like to use CSS alone to do this, but if I have to use some JS, I'm getting familiar with JQuery and am already using it in this site.

Thanks

Jason