First, I looked at html5rocks.com sources. Looks like trusted site. And they close tags there.
<link rel="shortcut icon" href="/favicon.ico" />
Then I looked at HTML5demos, and they don’t
<link rel="stylesheet" href="css/html5demos.css">
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It’s entirely optional. However, if you ever want to process a HTML5 file with an XML parser then i’d be inclined to include them.