It's good policy to do a final rinse with deionized/distilled water, regardless of where you live. The well water in Crystal Lake, IL, is very hard—the bedrock is either dolomitic limestone or pure calcitic limestone.
If you have a good water softener, that will take out the dissolved calcium, which is what makes water hard (limestone is calcium carbonate, dolomitic limestone is calcium magnesium carbonate). But the water softener will not reduce other mineral content to any significant extent.
Many wells in northern Illinois have water that is also relatively high in iron content. The two big suppliers of water softener salt (Morton and GE) both make a type specifically for use with high iron content water. You can also add a separate iron filter to your water system, as we did when we lived in Lombard, IL.