I don't know if 5 gallons is a magic number. I buy the biodegradable chemical drop-in packets. You can get them at Wal-Mart. No fuss or mess. Drop one in the toilet, fill the bowl with water and then flush. Now you are ready to use the toilet.
Allow a little extra water to run into the toilet with each flush. I also use
Happy Bowl toilet liners Works well and keeps the toilet clean. Use as little paper an necessary and make sure it is RV certified. It is the paper that will clog the pipes.
Then of course the key is to have the tank at least half full if not more when you dump. If you haven't used the toilet that much add water before you dump. It is the force of the water that empties the tank. After dumping, put in another chemical pouch before you leave the campground and you should be good to go.