Scandinavia encompasses three countries. I can tell you about Denmark and Sweden. In Denmark tipping is virtually non-existent. In Sweden you typically round up or give a small tip at restaurants or cabs. From my experience working bar one summer in Denmark, Norwegians actually offered small tips or rounded up -- partly because they thought it was so cheap relative to Norway! I have no idea about conventions in Norway.

If you pay by cc in Denmark then the amount presented on the bill will be the amount that you sign for. In Sweden you will have the opportunity to add a tip.

Finland is not part of Scandinavia, so no commment here.