jmc

The height of the pyramid is $12$ inches, so the height of the box must be at least $12$ inches. The base of the pyramid is $10$ inches on each side, so the minimum dimensions of the length and width of the box must be $10$. Since we want a cube-shaped box, we need to choose the dimensions of the box so that everything will fit inside. Because $12>10$, we want a cube-shaped box that measures $12$ inches on each side. (If we chose a box that measured $10$ inches on each side, it wouldn't be able to accommodate the height of the pyramid.) Therefore, the volume of the box is $12^3=\boxed{1728}$ inches cubed.