I just returned from a trip to Germany where I used ATMs 10 times. The first eight times were at Deutsche Bank at FRA, in a local bank in St. Goar, VR Bank in the Allgäu, Bayerische Bank and Deutsche Bank on Bodensee, Sparkasse in Rothenburg ob der Tauber, and Raiffeisen Bank in the Spessart. I never encountered anyone trying to get me to use Dynamic Currency Conversion.
But I did at Reisebank in Würzburg. And beware, they do it very subtly. A screen comes up with what just looks like they are summarizing the transaction. It's not like they explicitly offering you the convenience of handling the transaction in dollars, at 3%. And it's not immediately obvious that you have the option to reject it. The "Nein" button, at the bottom right, is smaller, and in a less contrasting color than the rest of the screen. If you press the softkey opposite "Nein", they will proceed with the transaction with no additional fee.