How do we core floated list items?

I have list equipment for my site nav that we need to center. I'm floating
so that we can have stuffing on a list items...setting them to inline
seems to discharge tip and bottom padding. #nav { width:100%; }
#nav ul { margin-right: auto; margin-left: auto; } #nav
ul li { float: left; background-color: #333; color: #fff;
padding: 15px; margin: 10px; }