I'd say you've inadvertently let him develop a pattern. He's found he can lie and the world doesn't end, it's comfortable, and now it's what he does... plus he's got a challenge, because he can see if he keeps trying, he may get good enough to fool you.
I wouldn't keep increasing the punishment. You'll either run out of stuff in your arsenal or the punishments will get too painful for both of you. Instead:
The first thing I'd do is break the pattern. Try as much as possible to avoid the trigger: any question to which he can lie. So, don't ask questions to which you know the answer to; don't ask questions when you can go check what the answer is, instead; and if you have to ask such a question, and you're pretty sure he's lying about the answer, don't let him dig himself in deeper. You're just challenging him by doing that. Literally. (Go read over what you've written.)
When he does lie, and these instances should be rare since you're not giving him opportunity, just sigh in disappointment/make a disappointed face (whatever; let him know you're not impressed), and tell him to do the thing he said he didn't do, or whatever. Don't punish him, or make it a nominal punishment, since it's not working anyway. Or raise your eyebrows: "Really? Was that smart to say that to get a cookie? How about may I please have a cookie?" You're not impressed. Move on.
At the same time I would shift the emphasis to telling the truth. Ask the librarians for books (picture books and harder ones) you can read to him where telling the truth saves the day. Where people relying on each other and trusting each other saves the day. Make up stories where amazing things happen when a child tells the truth.
I told my daughter about the Boy Who Cried Wolf, but she really loved to hear The Girl Who Saved The Sheep, which I told her after we'd done the other a few times. (It had all sorts of details, how she got up early and made herself a lunch, called the dogs, got the sheep out of the barn, took them up the mountainside... and when she ran to the village to get help from the wolves, everyone came right away, one man had a frying pan, a lady had a bull cutter (my kid's favorite outdoor tool)... and only one sheep was killed, but two dogs were hurt but they carried them back to the village and tied big ribbons on them because they were heroes, and they got well... etc.) I had to tell this story over and over again. I'm guessing that it was given extra savor by the existence of The Boy Who Cried Wolf; so I would make the truth-telling kid like him somehow, and the boy who cried wolf, not.
Start conversations about these stories.
"Gee, that kid did something really brave in that situation. He knew he was going to get in trouble for being out of the house, but he had to save the kitten... Do you think it occurred to him that someone else might come along and find her?... I hope I would be that brave, and not just hope someone else would do it."
"Wasn't it amazing how well the mom knew her kid? She knew not to believe the teenager about who really painted the car. I bet the teenager was surprised! I bet he got away with that stuff all the time with other little kids!"
And talk about white lies. Start a discussion about how you never know what to do when an adult has broccoli in their teeth. (My daughter was very intrigued with that one!) Ask what would he do. How about if it was a stranger? Or what if they'd just been onstage in front of a lot of people?
I'm not sure how subtle you need to be with this stuff; I started telling stories like this to my kid when she was much younger. At this point (ten years old) she has a very high personal integrity; the fact that she doesn't lie is a point of honor. And she's adept at the white lie, too; no one is more pleased than she when she opens a gift, no matter what it contains (unless the gift is from me, since she knows I need there to be truth between us).