I know it doesn't specifically answer your question, but my understanding is that a majority of 'we accept bitcoin' businesses use a service to translate it in

I know it doesn't specifically answer your question, but my understanding is that a majority of 'we accept bitcoin' businesses use a service to translate it in to their native currency at the time of sale (or very shortly after), and often will list their prices in the native currency (rather than BTC + constant adjustment).