I do agree that parameter-izing generic code is preferable to coding each case. I also know that, sometimes, it's clearer and cleaner to "code the cases". (And even then, I still try to parameter-ize a lot of the code into call-able functions.)

Out of curiosity, I asked one of our IT department's database gurus if she knew anything - or knew anyone who knows - about tax rate databases. 2 of her colleagues at other companies do work with tax databases. She told me that they use a lot of "stored procedures" and triggers to calculate the applicable tax rate for a significant majority of the scenarios the databases cover. Their rational is that this greatly reduces the complexity and size of the databases. Also, that even if they had to deliver a database with no stored procedures, they would have to write similar code to generate the parameters to store in the "pure" database.