For GLA adjustment, I round to the nearest $100 for anything $1,000 or higher. If the adjustment would be below $1,000, no adjustment at all. Occasionally for example I might make a $1,000 for one comparable, $2,000 for another instead of each adjustment based on per square foot. A buyer wouldn't--they might say to them selves, will this house has bigger rooms so I will offer $51,000 instead of $50,000 or this one has small rooms so my offer will be $49,000 instead of $50,000 (but then again the buyer might be making that $51,000 offer because they like the sound of the door bell). I also occasionally use what I call an "underwriter's adjustment" of $500--see underwriter I did make an adjustment for the subject's big porch versus the comparables small porch---it just doesn't have any effect on value which is $50,000 whether I adjust for that porch or not!