If you throw it away in a waste basket (Mitch recommends emptying the bathroom basket daily.....in her blog.
)...you can use whatever kind your heart (and bottom) desire.
Many of us do not put any of the toilet paper in the black tank. Especially if you are boondocking, your tank will last a lot longer ....i.e ....not fill up as fast.
If you just have to throw the paper down the chute, so to speak, you need to find one that is safe in septic systems....you need to use a lot more water and be very conservative on the amount of product you use.
Either way..."wet wipes" can be your friend....