Here is a thread I began a while ago about this issue:
DPP 3.0.2.6 and Jaggies on 1DIII files. It was about jaggies when converting 1DIII files using DPP. However I have also noticed jaggies from 5D files.
I quote from one of the posts:
"There used to be a jaggies problem caused by one of the DPP options.
If you look at Tools->Preferences, General Settings tab, make sure that the Viewing and Saving RAW Images option is set to High Quality."
However those are the settings I have always had and still see jaggies.
Raul.