Actually, fractions of inches or of pounds would not create a significant change on the result. So, don’t sweat the fractions.
With regards to your waist to hip ratio, perhaps you could re-run the calculator with 31″ hips to see if you change to a pear shape. BTW your weight is on the low end for your height and you may be premature in worrying about your “fat genes”. Your BMI is probably on the lean end anyway.
PS I designed the calculator because so many people asked what they should weight and how many calories they should eat. I figured people would like to tinker with the numbers themselves!