..Been in that spot many times. I prefer to dump at the end of all trips regardless (provided there is access to a sewer hookup or dumping station). Reason being, I've learned that if you let 'waste' sit in your tank for a long time (several weeks), even a small amount.....The smell coming from the tank next time you take the RV out can be very nasty (regardless what chemicals you use or don't use).
If black tank is only partially full at the end of the trip, just run water through the toilet, get the tank as full realistically possible with just water. Then, dump it. The more water in your black tank when dumping, the better. Thats what I do in that situation.