> The rules of multiple authorities apply to single jurisdictions.
There is no federal sales tax rule, so there is at most one soveriegn authority whose rules apply to any jurisdiction as to computation and collection of sales tax, any other authority is a dependent one, whose policies can be (and probably are already) constrained by the sovereign's own rules governing sales tax, which can be the level at which solutions are imposed, if necessary. "Thousands of independent authorities" is not a reality.
There is no federal sales tax rule, so there is at most one soveriegn authority whose rules apply to any jurisdiction as to computation and collection of sales tax, any other authority is a dependent one, whose policies can be (and probably are already) constrained by the sovereign's own rules governing sales tax, which can be the level at which solutions are imposed, if necessary. "Thousands of independent authorities" is not a reality.