Tartaras V was the fifth planet in its star system.

In 2369, the ruins of a Rokai provincial capital was unearthed. Quark suggested the planet to Vash as a potential source of valuable Rokain artifacts, which he could then auction for her. Vash decided to take him up on his offer. (DS9: "Q-Less")

This planet was only mentioned in dialogue.
According to the script, the pronunciation for Tartaras was "tar-TAR-uhs". [1]