Pub 531 p. 3 mentions a penalty for unreported tip income. Form 4137 calculates the soc. sec. & Med. tax owed, but it doesn't show a penalty. Where is the penalty found?

I see no forms generated as part of my TurboTax return that show a penalty calculation and I see no penalty entry on the 1040.  Does this mean that no penalty applies - possibly because of the amount of the unreported tips - even though they exceeded $20 per month?  Does anyone have more info on the penalty that is discussed on page 3 of Pub 531?