Bob Sturm has written two very nice articles on the Cowboys penalty situation. One can be access by clicking the title and the other is below.
These articles dispel a couple of myths that get repeated on BTB on a regular basis (or at least did during the Wade Phillips era):
1) the Cowboys have always been a bad penalty team, even under Bill Parcells
2) the Cowboys’ inclination toward costly penalties is somehow innate and therefore will not change.