In deciding Commerce Clause cases, courts must "make the delicate adjustment between the national interest in free and open trade and the legitimate interest of the individual States in exercising their taxing power, . . ." Boston Stock Exchange v. State Tax Commission, 429 U.S. 318, 329, 97 S.Ct. 599, 606, 50 L. Ed. 2d 514 (1977). The Commerce Clause does not require that all taxpayers be identically treated merely because they engage in foreign commerce, but rather focuses upon the burdens on interstate commerce. Caterpillar, Inc. v. Commissioner of Revenue, 568 N.W.2d 695, 697-98 (Minn. 1997), cert. denied 522 U.S. 1112, 140 L. Ed. 2d 108, 118 S. Ct. 1043 (1998). In determining the constitutionality of a tax involving interstate commerce, four factors must be considered: whether the tax is imposed on an activity having a substantial nexus with the taxing state; whether the tax is fairly apportioned; whether the tax discriminates against commerce; whether the tax is fairly related to services provided by the state. See Complete Auto Transit, Inc. v. Brady, 430 U.S. 274, 279, 97 S.Ct. 1076, 1079, 51 L. Ed. 2d 326 (1977). Where foreign commerce is involved, there are two additional factors that must be considered: 5. whether the tax results in an enhanced risk of international multiple taxation; 6. whether the tax impairs the uniformity of federal regulation of foreign commerce where such uniformity is essential. See Japan Line, Ltd. v. County of Los Angeles, 441 U.S. 434, 446-448, 99 S.Ct. 1813, 1820-21, 60 L. Ed. 2d 336 (1979); Barclays Bank PLC v. Franchise Tax Bd., 512 U.S. 298, 311, 114 S.Ct. 2268, 2276, 129 L. Ed. 2d 244 (1994). Broader constitutional protection against interference is afforded where foreign commerce is involved because "matters of concern to the entire Nation are implicated." Kraft Gen. Foods, Inc. v. Iowa Dep't of Revenue & Finance, 505 U.S. 71, 79, 112 S.Ct. 2365, 2370, 120 L. Ed. 2d 59 (1992) citing Japan Line, Ltd., 441 U.S. at 445-46, 99 S.Ct. at 1819-20.