Khepera spends all day pushing the sun boat across the circle of the heavens. All the gods and goddesses in the circle clique have important things to do with this lovely round shape, and you probably don't want to distract them. The Earth's life may depend on it.
Khepera's fellow K-god from Egypt keeps track of an important circle: his potter's wheel. And he sure is good with his hands; on that wheel, he creates the souls of mortal men and women. Talk about well-rounded individuals. (Hey-o!)
Greek Atlas is in charge of a huge circle: putting the sphere in atmosphere. Zeus punished Atlas's rebellion by sticking the sky on his back. Khepera apologizes to his pre-Olympian friend every time he and Ra cross the sky. He knows exactly what it's like to have a big burden on your shoulders.
The Norse goddess of the Vanir keeps a special circle. It's called Brisingamen, and it's a magic necklace, specially crafted for her by the dwarves. Even Thor borrowing it and Loki stealing it couldn't break the circle, though one time, Freyja got so angry that it snapped right off her neck. (Oops.)