It really depends how much money you are willing to spend, and how much trouble you are willing to go to. Probably your simplest option would simply be to get "full spectrum" fluorescent tubes. You do have to be somewhat cautious though, because many companies claim their products are "full spectrum", but they really are not. Some are much better than others. I would recommend TrueLite brand. The only downside is that the special phosphors they use degrade faster, resulting in gradual color shift, and it is recommended that the tubes be replaced much more frequently than regular fluorescent tubes.
LED is becoming very popular now. For commercial spaces, where better light quality is desired, "high CRI" LED lamps are now available. These are used in the fruits and vegetables section of grocery stores. The main difference with "high CRI" for LED is that it is better at rendering red colors, such as fleshy pink skin tones or red apples, and the light has a warmer feeling to it (has nothing to do with how yellowish the light is).
In some situations, a commercial space may be using both halogen spotlights with LED overhead. In this case, it is not as important to use "high CRI" because there is already so much red frequency light in the spectrum given off by the halogens.
Halogen is generally regarded as having the best quality of light (besides natural sunlight), though this normally is not practical in commercial spaces for several reasons. What some higher end commercial spaces will do, however, is use a combination of halogen spotlights to shine on selected displays, with some other type of lamp to provide most of the lighting in the store. If you are using a large number of halogen fixtures, another thing to consider is the heat. In warmer climates, this could increase the cost of air conditioning, while in very cold climates this may be an extra benefit.
It costs more, and has to be special ordered, but there are ceramic metal halide fixtures. These operate similar to metal halide, but have better quality of light and are appropriate for indoor spaces. If you want a cooler color of light, and the highest color rendering available, ceramic metal halide can be the next best choice (besides natural sunlight). The economics of ceramic metal halide generally make it more attractive in situations where very large amounts of light are required (athletic fields, sports stadiums), but they have been used in high-end small-scale applications, particularly landscape lighting.
Depending on when your store is open, you might see if it is possible to install sky lighting to let in sunlight. Sunlight is the best type of light, and the most energy efficient, obviously. During the dark evenings other types of light can be used.
One extra little thing most stores do not consider, if fluorescent tubes are used, they leak out some UV radiation. A very small number of people are especially sensitive to this, but it is probably not the best for anyone working under them all day (there was a study that showed a link to increased risk of cataracts). Make sure your fluorescent fixtures have plastic diffusors over them, this cuts out more than half of the UV. If one was really concerned about this, there are special UV blocking plastic tubes that can go around the fluorescent tubes. For example, if there are bare exposed fluorescent fixtures right above where the employees are stationed, it would make sense to use the UV blocking tubes there. For a typical customer that only spends 20 minutes in the store, this is not an issue. Some high end clothing or art stores take precautions because the UV can cause colors to fade over time.
Consider this though: artificial lighting tends to make colors look off because it has an incomplete spectrum; it only gives off certain color frequencies of light. So if you use two different types of lighting, that can generally improve the spectrum coverage, leading to better color rendering.
