George,
The rounding of of the overcurrent protection does not change the ampacity of the conductor. Any place that the code calls for a conductor of a minimum ampacity, that must be the ampacity of the conductor under the conditons where that conductor is installed. Remember that 310.15(B) tells us that a conductors ampacity shall be as specified in the ampacity tables as modified by (1) through (6). The temperature correction factors are part of the ampacity tables and the adjustment factor for more than 3 conductors in a raceway or cable is 310.15(B)(2).
This is an ongoing problem with the use of the code. In the 2005 code they changed the wording to say that you cannot use the provisions of 240.4(B) for tap conductors. This was not a rule change, but so many code users were missing the fact that 240.4(B) does not change the conductor ampacity. The tap rules are like the rule that I cited in 440.32. They require a minimum conductor ampacity. Some additional sections that require a minimum conductor ampacity are 424.3(B), 424.82, 426.4, 427.4, 430.22, 645.5, 669.5, 680.9. In all of these cases the rule requires a branch circuit conductor ampacity of 125% of the nameplate current. In all of these cases that conductor would have to have that minimum ampacity after the application of the adjustment and/or correction factors.
If the code section that covers a installation does not require a minimum conductor ampacity, then you are correct and the provisions of 210.19(A)(1) apply. The don't apply where other code sections set a minimum conductor ampacity.
Don
