Is there a way to match the height of list elements?

Is there a way to match the height of list elements?

I have an un-ordered list, there are 3 li items per line and 5 lines. The
content of each li is dynamic and if their is more content in 1 li item
then the others it will push all li items after it down. Is there a way to
stop this happening, so if an li has more content then each li on that
line will match it's height and thus making everything line up?
I've included a link to the code - http://jsfiddle.net/3YTbK/4/
And I've found this which makes everything line up, but I now need to
figure out how to stretch the height of the in line elements:
ul > li:nth-child(3n+1) {
clear: both;}