rounded decimals?

FROM : Brett O'Donnell
DATE : Thu Apr 07 22:52:21 2005

(Sorry if this is a newbie question)

What is the easiest way to round a double number to a certain decimal
place?

The line is currently

   [textRho setDoubleValue:rho];

Thanks in advance for any help you can give.

Thanks,
Brett O'Donnell