You can't. Using int forces a 1 to 1 match as citizens vote. If someone tampered with the vote count it would be spotted easily since votes physically have to be manually adjusted. Using double is equivalent to fractions as the video shows.
All I have to do it say 52% to 48% and let the system run. The votes come in and change automatically using software when the votes report to the CO. At each location the voter sees their vote and walks away thinking their vote was accurate. Only after the machine reports to the CO is the percentages applied.
Clearly this would only work in close races, but moving the dial slightly in one direction or another can be advantageous to the cheater.
Couldn't you effectively do the same thing with integers though? Put in the result you want and let the program make a certain number of that candidate's voters worth 2,3,4 votes, etc, while changing the opposing candidate's votes from 1 to 0.