I got my girls as point of lay chooks, and one of them started sneezing shortly after they arrived. (No runny nose or eyes - just an occasional sneeze). When the other two started to sneeze as well, I panicked (being a newbie chicken owner) and I went to the vet, who gave me antibiotic powder for them. I now regret using it, as I had to throw the eggs away for a fortnight, and although they seemed to sneeze less afterwards, it hasn't stopped it completely. I feel it was a waste of time and money, and just completely unnecessary.
I think it's a combination of chilly weather and dust (they have wood ash in their dust bath) that causes them to sneeze. They all have an occasional sneeze once or twice a week (that I hear, although it could be a bit more since I'm not with them all the time), but since they all seem in perfect health otherwise, and are laying well (although Rusty's broody at the moment), I'm not worried any more. In the absence of runny noses / eyes or other symptoms I would be inclined to leave well alone and just monitor them.