Let me give you a shove to increase your lean :)

Since you are clearly working with an RDBMS for your store, you really do want to have a relational model for your data that is fully normalized. Since you note elsewhere that this application will not involve either a huge database or high transaction rate, you probably do not need to spend resources on premature optimization.

So long as your classes properly assemble the data, the outside world has no need to know what wizardry goes on under the hood.

yours,
Michael