Are there any aerospace examples of applying a boat tail?
This depends on the mission the plane is built to fit. Some planes need the cargo space so the tail is less tapered but most planes have at least some taper. Diamond Aircraft have very tapered tail sections 


(source)

Even the older GA designs like the Piper Seminole have a good deal of tail taper 

(source)

Larger planes have some tail taper as well however sometimes there is less as there are often systems in the tail like the APU or there is storage space.


(source)