lat-long coordinates

I have been killing myself trying to figure out why my
kriging routines quite often bomb out (for no apparent reason).
Well the answer is that I often find that I have two (or
more!) identical coordinates because even though I read in
site lists with a precision of 1/1000 of a degree GRASS
only keeps the first decimal place!

long lat value
143.345 -12.012 343.2 <---this is what I enter

143.3 -12 343.2 <---this is what GRASS seems to store

If this is true it means I cannot usefully use geographic
coordinates where I have a spacing less that about 11km
(one tenth of one degree)! Now what have I done wrong,
because this can't be correct?