The result ensured that the club advanced to the quarter-final stage of the Heineken Cup, where they will face Harlequins in the next round.
"We were up against some pretty resilient opposition and the boys delivered a pretty compelling performance at times," Penney told reporters.
"We made a couple of errors early on and that was on the back of being a bit anxious and wanting to do well. It took us a bit of time to settle into the game, probably longer than we would have liked.
"Once we got into our rhythm, I thought at times we were compelling. We looked very efficient. Our mental preparation and ability to stay focused for the whole 80 minutes was something we were going to need today. The relentlessness we were seeking was there."
Munster's win eliminated holders Leinster from the competition.