or you could reopen it and as soon as the next (tie breaking) vote comes in close it again.
That's true, but what happens when I'm not here to open the poll and wait? Hmm.. I've got an idea. How about the first post that is posted after the poll closes with a person voting for one of the two sports wins. Like: "I can't vote because the poll is closed, but since it's a tie I'd like to break it by voting for Sport X." That should work since the poll closes at a specific stated time. It would be easy for me to compare post times with this time.