That's BS!
I did the routine in DaNang...Including the paperwork to get married...I don't believe more than 1.5 million ever passed across the counter for anything. One million was for the initial paperwork and that only took a week or so. I think the medical bill to prove I was crazy was about 125,000 vnd and that was listed as being such. The only 'gratuity' that I have paid was to the two women across the counter for their help after all was done...a bunch of flowers for each of them.
I've lived here in DaNang now over 4 years and have never had to pay any 'coffee money'...to any official in the City.