Years ago I bought a 15 gallon tote, because so many people here said it was a necessity. Then I realized that most campgrounds where we dry camp didn't have a dump station, so it was useless.
It sat under the workbench out in the shop for years, until I sold it for $5 in a garage sale.
My point is, before spending the money on such a thing, be sure it is usable where you usually camp. It isn't much good when the nearest dump station is miles away!
Conserving fresh water and using the provided (if they are) vault toilets helps avoid filling the waste tanks.