Spoke Length Help - First Wheel Build
You do have some margin for error with spoke lengths, so do round off fractional lengths.

For spoke type, a double-butted 14/15/14 spoke would probably be ideal, short of that a straight-gauge 14-gauge spoke (straight-gauge is cheaper; double butted is preferable because it puts extra material where you need it, so the spoke is more evenly stressed over its length). If you feel you really need something beefy, go for 13/14/13, although that may be harder to find. Get stainless spokes and brass nipples (aluminum nipples are more prone to corrode). 

DT and Sapim are the big names in spokes. The only spokes I've seen that I would specifically dis-recommend had S-hooks at the end instead of a J-bend (and those were hooked because they were aero spokes, so probably not an issue for you).