2000 mustang gt digital odometer problem

I have a digital odometer in my car. Recently the odometer would start to round itself to the nearest half, for example, the odometer would say 78,008.7 miles on it when i shut the car off but i turn it on no less than 30 seconds later and it would read 78,008.5 and the tach would zero out. I have checked all the wiring that leads to the gauge cluster and have found nothing. Anyone know what is going on? I appreciate anyone's input. Thanks.