When you are in the process of working with your images, it can be considered "best practice" to keep your images in "high quality" files, so the tiff or psd formats are best for that, rather than jpegs which have been compressed in two different ways. Your tiffs can be either 16 bit, which have the fullest range of image data, and CS5 can work well with them up to a certain point, or 8 bit, which you can eventually convert to and have a smaller file size.
Your final output can be saved as a jpeg for print or other uses. For printing some labs will accept a tiff, but if you save a full size high quality jpeg as a final product you really won't see a problem. People run into problems with jpegs when they either save one multiple times, causing multiple compression episodes, or they over-compress and then try to get a large print.