If someone rented a car and caused a small amount of damage to the car. It could be it’s so small the rental company won’t notice it at all. However if they do notice
it or are made aware of it, could be they would charge the person more money than it costs to fix it. In this being the case does the person have to tell the
rental company about the damage since he is afraid that perhaps they will take more money from him?
I assume that the contract made with the company obligates the renter to inform them of damages, and in this case you will have to tell the company. The company also has to go by the rules concerning making payment claims, and I assume that these are also clarified in the contract on elsewhere.
If there is no such obligation (of informing the company), you can rely on the salesman who will look over the car before receiving it back. Of course, you have to answer all questions he asks truthfully.