Just a word - when you have dancers ... they never mind if you stay in tempo. The other way to do it on the fly is to program the ritardando into registrations. Does your keyboard have a "rit" button? You can preset that to your custom ammnt in some cases too.
For me, I just stay in tempo till I need to punch the very last few hits and I turn off the drums at that point and just use a solid LH bass layered over the chord sound du jour (I change that alot). Nice and full, with a dynamic ending, and the dancers get a few extra measures of ateps in!