It's usually a good idea to acclimate fish by adding a little tank water to the bag every 10 or 15 minutes while you float the bag, after the temps are equal. Unless you're sure the water at the store has the same parameters as yours, fish can suffer from pH or hardness shock when you add them to the tank. More sensitive fish can really suffer (even die) from this, but hopefully your swordtails will deal with it well.