Most ball powder will throw to about the accuracy you mention with standard measures, and with a benchrest measure you can stay within 0.1 grain. That said, keep in mind that about 0.2 grains of difference in water capacity of a case will have about the same effect as changing powder charge 0.1 grains. 70:30 cartridge brass is 8.5 times the density of water, so your brass weighs +/- 1.7 grains, it will have about the same effect as a varying the charge +/- 0.1 grains. You want to trim your cases (the factory often doesn't do a very consistent job) and cut the primer pocket bottoms to uniform depth and deburr the flashholes before weighing so you start with dimensionally similar brass, and the weight variation then reflects the water capacity more closely. If you want the case volume variation to be insignificant compared with the powder, you probably want to sort it tighter than I just mentioned. Say, +/- a grain. Half a grain if you are benchrest shooting.
After you've done all this stuff, the next trick is to find a load that is relatively insensitive to charge weight error in the first place. Take a look at Dan Newberry's
Optimum Charge Weight site.