Tippet is not commonly matched to the weight of a fly rod. It is more common to match your tippet to your leader or to the type of water you are fishing. When fishing for bigger fish you often need to use stronger tippet. If fishing in clear, shallow conditions it's often necessary to use tippet
It's very important to match your fly line to your rod, it would be a large error not to do this - check out the article in the related link for more information on fly lines.