Randy,
Latitude and longitude as in the form xx.xxxx is a choice. UTM projection is another one. There are at least 5 projection schemes. Precision is important but as I could see not a much concern for you.
You think to work with zipcodes, then good news :) you could even drop lat, long. MapObjects have a AddressMatcher object. It has PEM from country level to housecoordinates level. You'll see that when you look MO help and I think will have a better understanding what to store. You're lucky you'll do this for US where ArcInfo maps are ready with exact coordinates. You might easily just store address data and show it on a preready map :) (Also there is a tracking layer on which you could follow your trucks moving along the streets- funny).
Cetin