Here is a fascinating article about the history of the idea that the pyramids were grain stores.
There is no mention of pyramids in the Bible's version of the story but in the Middle Ages people started to write them into the story. "If you go to St Mark's cathedral in Venice, there's a medieval depiction showing people using the three great pyramids of Giza as granaries in Joseph's story," says John Darnell, a professor of Egyptology at Yale University. "If you didn't have access to the structures, the idea had some currency." The belief was also popularised by Saint Gregory of Tours, a sixth century Frankish bishop, who wrote: "They are wide at the base and narrow at the top in order that the wheat might be cast into them through a tiny opening, and these granaries are to be seen to the present day."
But Darnell says the idea began to fall out of favour during the Renaissance, when people made more detailed studies of the pyramids.
Egyptologist James Allen of Brown University [says] "There's no way in the world an ounce of grain would be stored in a structure like that. It would be totally impractical. It's like saying the Tower of London was built as a granary store."
For details of why the theory is now discounted, see Gordon Stranger's excellent answer.
There seems to be no hint that any modern Christian groups hold this view as a matter of doctrine.