Of course, just take the contents of all of them, and stick them into one (or a new one). Then, just make sure all your pages have a link to it.

Do know, if you're combining style sheets and you have some property: value combinations that are the same, which ever is lower in the file will take precedence. Like this,

Say you have:
#leftCol {
width: 250px;
background-color: $ffc;
}

#leftCol {
width: 270px;
background-color: $ccc;
}

Then, your site will always show the lower set of values, because it is physically lower in the code.

You may not have repeating values, but it can be common when merging css files.