Within the past year I've taken up graphics programming with OpenGL and have made Blender my preferred tool for creating obj models to load.

Right now I need a cube and I thought I could use Blender's default cube. This may sound nitpicky, but my output OBJ contains seven normals instead of six, and a corner is off slightly (off by 1.0e-5 units). Blender says my corners are correct though. Can I avoid this error somehow? Having axis aligned normals is something I want right now.

You could just compute the cube's on your own if you want it perfect (its 8 vertices, 6 normals, and with some organizing to get correct per vertex normals for proper lightning you get 36 vertices and 36 normals).

A function to generate that kind of geometry is always useful to have around (along spheres, cones and cylinders).

Blender handles arbitrary units (even meters, inches, etc), maybe there is some unit conversion going on. And 1.0e-5 is 0.0001, pretty small, you could do the rounding on your own at load time too.

Just curious: what's the seventh normal attached to?