Munster trail second-placed Glasgow Warriors by a single point heading into their final clash of the regular season against Ulster next weekend.
If they were to overturn their rivals from Scotland in the table, it would seal a last-four clash at Thomond Park.
But Penney says there is still plenty of work to do after watching his troops underperform in the first half at Meggetland.
The hosts took the ascendancy early on through Carl Bezuidenhout and WP Nel, but Andrew Conway had responded before Denis Hurley danced over with half-time approaching.
And Munster turned the screw after the break, as Damien Varley, Duncan Williams, Tommy O'Donnell and two penalty tries saw them home to a 55-12 victory.
"It was pretty convincing in the end," said Penney. "But we made quite a few first-half errors.
"We'll have to improve for Ulster next weekend."
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