I've become fairly familiar with half point values in the different American sports but still fail to come up with solution for soccer.

Ex: Team A -0.25 at -105 should equal to how much + money at -0.5? Is it always the same difference or do the books adjust according to the total for example?

My first instinct was to look at the Pinny drop down box but I know they add vig for the American sports (same for soccer?).