Effect of parasitic load on in car battery float charge voltage?

A question for general education purposes...

According to Wikipedia the float charge for a 12V AGM is 13.6V. That is, the voltage necessary to push enough current into a battery to exactly cancel the self discharge, and the battery should be able to sit like that "forever". It would apply as is for a battery not in a circuit. However, I mostly charge batteries when they are electrically attached to the car. So if the car has a parasitic load of 25 mA, which is roughly what is measured on our 2007, how much higher would the voltage on a charger have to be to maintain the battery fully charged?

My gut feeling is that it is probably no more than .1 or .2 V, but I don't have any data to support that. I suppose I could charge the battery in circuit and out of circuit and compare. Not sure it would answer the question though, as on our 2007 Prius the 4A Viking charger (the one which is really only 2A at 12V) tends to sit oscillating at 13.8-13.9V for a very long time once the battery is mostly charged (over 90% SOC). The backlight is still on, so it doesn't "think" that it is float charging yet, but it is really close at that point. The noise from this oscillation could easily be as large, or larger, than the delta V resulting from the small parasitic load.