To each their own. In simple lists for navigation menus I always omit closing li. There is no ambiguity on what I am intending even with those closing li omitted in such simple cases:

  <nav id=main-nav>
  <ul>
  <li><a href="/">Home</a>
  <li><a href="/hamburgers/">Hamburgers</a>
  <li><a href="/sausages/">Sausages</a>
  </ul>
  </nav>