Cannizzaro notes that the Roth TSP is particularly advantageous for working people who expect to pay a higher percentage in taxes in retirement than they do now.

"If you are going to be, when you retire, in a higher tax bracket, then it does benefit you for sure," he says.

Cannizzaro is a retirement planner with the investment advisory firm of Ticknor, Atherton and Associates.

While there are a number of estimators out there, Leins recommends using OPM's Federal Ballpark E$timate to help workers figure out how much they need to save in order to have a comfortable retirement.

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