It's almost always used as "sword and sorcery", only a single sword. The current tag "swords and sorcery" is a misspelling.
I am strongly in favor of correcting it to the actual term.
I'm not all that familiar with this term, but a quick check on Wikipedia suggests that "sword and sorcery" refers to the subgenre of fantasy while Swords and Sorcery refers to a particular work within this subgenre.
Since all the questions with the tag on this site refer to the subgenre rather than the specific work, I've changed the tag name to sword-and-sorcery. If we ever get questions about the specific work, we may have to think again, since I'm not sure if the system will allow two such similar tag names.