As mentioned above the chamfering is important for all PVC connections, however you don't have to do it quite to the extreme you see in the pics above. Just a little bit of sanding to knock off the sharp edge is really all that is needed. The whole purpose of rounding it is to prevent the sharp edge from scraping away the glue as the pieces fit together.
FWIW, I definitely do this if I'm working on any PVC for my house. For tanks, I do it if it's a pressurized connection like that used for return pumps or closed loops. I don't bother doing it for drain lines because those are never exposed to any pressure and therefore their chances of developing a leak after gluing are very small.
