In my book this is rather formal and oldfashioned. It lays itself open to two interptretaions, I would say.
It could be a final salutation - I’m off, I’m going, ta ta, cheerio, see you
It could also be a final salutation with a sting in the tail. It reminds me of an occasion of a deal I did or rather didn’t do with a car salesman. He had agreed certain points and when it came to the handing over of my car and the taking over of his car, he reneged on one major point. I then somewhat dramatically tore up the contract and walked out of the showroom with those words: I wish you good day. I didn’t half feel good.