That is a misconception (on both accounts) from popularised science. Tachyons are hypothetical and would travel faster than the speed of light. If they exist, then you could in principle use them to send a message to your past. Whether or not they "travel" backwards in time would be a question of reference frames.
Anti-particles are a different story all-together. There is a very particular sense popular science authors are using to say that they are "particles traveling backwards in time", but they very often fail to specify what that sense is. Anti-particles are associated with the corresponding particles and have the same mass. They travel at subluminal speeds (or at light speed if massless). Tachyons have nothing to do with normal particles and would travel at superluminal speeds.
