Tax evasion was the secret ingredient at throwback-themed restaurant chain Nifty Fifty's, prosecutors said as five of its top managers were sentenced this week for bilking the government out of $2.2 million.

Co-owners Robert Mattei, 75, of Delray Beach, Fla., and Leo McGlynn, 53, of Swarthmore, admitted they failed to account for $15.6 million in revenue between 2006 and 2010 and routinely paid employees and suppliers in unreported cash.

In a series of hearings this week, U.S. District Judge Mary McLaughlin sentenced Mattei to just over a year in prison and McGlynn to three-year stint. Additionally, three restaurant managers received sentences ranging from one to two years for their role in the scheme.

To date, the group has paid $4 million in back taxes and an additional $205,000 in forfeiture payments, prosecutors said.

Nifty Fifty's operates eateries in Ridley Township, Bensalem and Northeast Philadelphia as well as two locations in South Jersey.

Jeremy Roebuck