Both spellings are equally correct. When you use the word as an adjective it means coming soon or happening at the moment. (He will arrive some time toward(s) the end of the month) But when it is used as a preposition it can mean different things depending on the context. It can mean in a certain direction, (moving toward(s) the right side of the road) or relating to something. (She tends to be more helpful toward(s) young children) and so on.