At 5 years old it's likely to be a habit.
There's some research that shows that "pre-school" (It doesn't put an age, but id say under 4 years old or so) children have a need to feel comforted to go to sleep. Many children get that comfort independantly and without a parent. But there will always be children who get their comfort soley from Mummy and have no other ways to feel comforted and secure at bedtime.
So up to about school age, while your DS could have been encouraged to transfer his comfort to something that doesn't require you (teddy, thumb sucking, ear tickling etc), by now he shouldn't actually need that comfort and it's likely to just be habit.
So I'd do Rapid Return and also a reward system.
Rapid Return means being quick about taking him back to bed, no messing around settling him and be consistant and relentless about it.
Talk to him about it lots in the week oeeceeding starting. Make sure he's very clear what will be expected of him and what will happen if he doesn't comply. And give a countdown of days until it starts.
Develop yourself a mantra, for example "Sleep time now. You lie quietly in your bed at sleep time. Nan night". Every time he gets up in the night, wake yourself up and get up (or DH gets up) straight away and immediately return him to bed. Say the mantra while tucking in, give kiss and leave.
Close the door. He needs to embrace the fact he is staying in his room alone. So make it non-scarey. Night light, whatever he needs.
If he cries, or gets up again - repeat. Back to bed, mantra, leave. Repeat over and over and over and over again. Consistency is key.
Don't start the reward chart strsight away - he is likely to "fail" the first few days so it would just be disheartening. After a week, maybe a few days, start a reward system for staying in bed all night.
I would give an instant reward if he stays in sleeps all night in his room. Biscuit when he wakes up for example.
Then offer an incentive to not only sleep in his room, but also to not wake you up in the night. Pick a toy he wants from the Argos catalogue, cut it out.
But some special giant stickers. Make space for 10 stickers around the edges of a piece of A4 and stick the toy (he picked from the catalogue) in the middle. Ten uninterputed nights and he gets the toy.