In most places on the site you're shown an average. So no, the average score doesn't jump. It changes smoothly as you get more ratings.
Now, speaking as a player and creator, star rating systems are iffy. Five are already too many. I think people only ever give one-star ratings out of spite. I only rarely give a two-star rating, and I often hesitate between four and five. Worse, I assign my own meanings to each rating, and so does everyone else, so it's ultimately meaningless.
Also, the system has been abused so often, and has caused so much bad blood, that it's set to be replaced with something else entirely.