You are probably going to have to put a helper column with you data.
Something like this:

=if(C7 < .05,"<.05",if(C7=.05,"=.05",".05")

Then include that column in your pivot table and put it in the row
section.

You might be able to finagle this into a calculated item, but excel is
pretty strict on what you can do with a calculated item.