You can stop where you want with microstepping if there's negligible friction
and keep powered up.
Microstepping doesn't give you the accuracy you think though, since the motor shaft
will not be precisely at the centre of the stator (in a cheap production stepper), this
slop is normally quoted in the specs.
Also the microstepping response of motors is not linear between full-steps, its a bit
wavy. Microstepping gives you some more resolution and a lot less vibration, which is
important for fast moving systems.
If you want really good accuracy you need an expensive optical shaft mounted encoder and
closed loop control.
You aren't looking for high accuracy at all, high accuracy means more like 2^16 steps
per revolution or better! check the motor specs - something like "+/-5% of step size" or
some such will be quoted if the motor has a good datasheet.
If you can find a nice 0.9 degree step motor you'll get to 0.45 degrees just with half-stepping