jrochte (sorry for not giving a complete answer earlier)
To change an existing dimension style, select it first. Then look at the top of screen for something that looks like NUM.DINCH or NUM.DMM. These are the dimension syles (graphisms) and you can change them by using the down triangle to choose a different style.
On the right of the style is the precision. It's probably set to something like 0.01 Again you can choose a different precision setting from the list, or you can click the panel and type in your own value. '8' will round off your inch dimensions to the nearest 1/8" and '16 will round them off to the nearest 1/16"
You can probably find the same options if you go to the properties of the dimensions.
Follow Bob and Jim's advise to set up your own standard, so your dimensions will be added with the correct graphism.