On the parent site there are currently 3 questions tagged with rythmbox and 3 questions tagged with rhythmbox. In general, I would say that the former questions should be retagged in favour of the correct spelling. However, this appears to be a very common slip (and is very easy to do in this case) so I am wondering if anyone else thinks a tag synonym might be useful instead?
In this case, I would say: Fix it.
I don't think we should lower the quality of the site. Anybody who can, should fix typos when they see them be they typos in tags, titles or posts (even answers).
Someone has fixed the rythmbox tags.