It does not print bar codes on checks, nor does it print them on Contribution Statements. There are some specific USPS guidelines as to what qualifies for bulk mail rates and personalized things (not the same piece mailed to everyone) are not considered bulk mail.
I'm not an expert on this by any means, but that is my understanding of it. You should do more research into the USPS guidelines for more details on those types of things.
http://pe.usps.com/text/dmm300/DMM300_landing.htm