<span> is an inline element. The term hanging indent is meaningless unless you’re talking about a paragraph (which generally means a block element). You can, of course, change the margins on <p> or <div> or any other block element to get rid of extra vertical space between paragraphs.
You may want something like display: run-in, where the tag will become either block or inline depending on context… sadly, this is not yet universally supported by browsers.