I used to put a class of .last on the ending list item or anchor link in my menu’s so I could remove the right margin and have it neatly lined up with the parent container’s padding. In the spirit of progressive enhancement, I now use the following line. I also use a similar trick on vertical menu’s or accordions but for removing the bottom border.

.nav li:last-child a {margin-right:0;}

For a nice demo, inspect element the top nav on this site!