Compass declination???

Ok this should be a simple thing to do but its not... Is there away to input a declination like 2.12??? only seem to be able to round off.. so that would be a dec of 2 that would not be too bad but if its 2,57 for instance then that needs to be inputted by at least 2.5 if it was possible.. SO can we do it?? and if so how??

regards

Grags