Not sure if you mean
sumImage = (double(bw1) + double(bw2) + double(bw3) + double(bw4) + double(bw5)) / 5;
or if you mean the union of all of them with the result remaining a binary image:
binaryImage = bw1 | bw2 | bw3 | bw4 | bw5;
Which is it? Or a better question would be, why do you want this image? What are you going to do with it?
If you would have 5 binary images stored in the variables Im1, Im2, Im3, Im4 and Im5, than you can get the summation by the command:
ImSum = Im1 + Im2 + Im3 + Im4 + Im5;
The new image ( ImSum ) will probably no longer be binary. You can normalize it to have its mean equal to 1 by the command
ImSum = ImSum/(mean(ImSum(:)));
Is this what you were looking for? You should try to be more specific in your question, i.e. post an example of what you are looking for or provide us with more details...