It is OK to throw toilet paper in the toilet as long as your sewer pipes are in good shape.
Toilet paper is meant to be thrown in the toilet and flushed down the drain.
The toilet paper is designed to dissolve in water so it can easily pass through the toilet and sewer lines and is mostly dissolved by the time it reaches a septic tank or city sewer system.
If you have old sewer pipes that are prone to clog then the toilet paper may cause an issue but for most plumbing the toilet paper will not cause any issues.
I've always thrown toilet paper down the toilet and never in the trash can.
It's actually disgusting to throw toilet paper in the trash can and can spread germs so always throw your toilet paper in the toilet and flush it away.
Just avoid putting too much toilet paper down the toilet at a time or it may clog but in normal amounts the toilet paper should cause no issues with your sewer system, toilet or septic system if you have one.