Tomato sauce usually has enough acid to keep the Ph low even when there are finely chopped peppers and onions in it. It certainly doesn't hurt to pressure can it. I pressure can everything except canned half tomatoes. Pressure canning cooks them too much for me. If I want stewed tomatoes I like to cook them that way.
Here's my methods of canning......
Hot Water Bath Canning 101:
http://www.hotwiredgardens.com/pdf/C...or_Dummies.pdf
Pressure Canning 101:
http://www.hotwiredgardens.com/pdf/C...or_Dummies.pdf
A pressure canner is the best investment a gardener can make.