A 5 year old should be able to wipe themselves as long as they don't have any disabilities.
However even a normal developing 5 year old may have some trouble wiping themselves and may need some help in some cases.
My 5 year old sometimes needs help to wipe his butt after he poops as he sometimes doesn't clean down there very good and sometimes he even forgets to wipe so I have to ask him if he has wiped after pooping.
If not I have to send him back into the bathroom to wipe and sometimes will help him regardless.
It's okay if a 5 year old needs some help with wiping themselves after they poop but they should be able to wipe themselves at least some and some 5 year olds have no trouble wiping themselves.
When I was years old I always wiped myself and did a good job at it but it can vary from child to child.