Ah. I'm afraid that Eraser does not at present have that capability. It might be possible to write a script to select and delete files to the Recycle Bin, then erase that, but my instinct is that that would be more trouble than it's worth.
The Eraser plans for 2011, which I have discussed with Joel and Garrett, include the development of plugins to erase particular file sets (including those associated with browsers and other apps.) Your requirement seems to be an ideal candidate for this approach. Why not sign up to Trac and create a ticket for a feature request? Trac is very much Joel's 'to do' list, so is the best place to ensure that new ideas are not forgotten.
David