Using A* and still avoiding collisions?

I am designing a tower-defense game, and for that I am using the A* pathfinding algorithm to reach my destination from my spawn-areas.

The problem here is that all the units stack, which doesn't look visually good. Is there a way I can make them somehow group instead, and spread more if there's not enough space?

The algorithm works so that all units move a single tile at a time.