The Bookies Over-Round on a match can easily be calculated. You just divide each of the individual Odds for the Home, Draw and Away calls into the number "100", then add the 3 separate results up and subtract that total number from the number "100".
Let's take as an example a match where the Odds for the Home/Draw/Away are 1.25/6.00/10.00. The 3 separate results from dividing each of the 3 Odds into 100 are 80.00/16.67/10.00. Adding those 3 numbers together gives you 106.67, and subtracting that from 100 gives you 6.67. The Bookie's match Over-Round is therefore 6.67%.
However, don't let a low match Over-Round fool you into thinking that you've got a bargain bet, because the Over-Round is not meant for that purpose. The Over-Round is simply the mechanism the Bookies use to make sure that, overall, they are offering Odds that will not cripple them and are not so unattractive that Bettors are driven to put their money with Bookies offering a better deal.
Bookies know that Bettors quite correctly look at the Odds on offer for the Call Type they are interested in (Home, Draw or Away). And when it comes to a Favourite (a so-called "sure-fire winner") playing, the Bookies know that there is a 75% chance of the Favourite winning. So what the Bookies do when the Home team is the favourite to win is offer much lower than fair Odds on the Home Win call, and increase considerably the Odds on the Draw and the Away Win calls, in order to attract more people to put their money on those alternative calls.
That way, because the Over-Round is still maintained, the Bookies hope to come out on top no matter which way the actual result turns out. So now you know that a low match Over-Round has nothing whatsoever to do with fairer Odds being offered - it just means that the Bookie is being very clever!
What you should be looking for is where the Over-Round for a particular Call Type (H/D/A) is low and where the Probability for that Call Type is over 50%, because that indicates a possible Value Bet. The problem is that you must have a valid means to establish the Probabilities for each of the Call Types in order for the existence of a Value Bet to be genuine, and that takes a lot of work. Trying to calculate Probabilities for themselves will be a nightmare for most people, and finding a good soccer betting advisory service to do that for them is a much easier way to overcome the problem.
One last thing to remember with possible Value Bets is that they exist because the Bookie has not seen them! And the Bookie is most likely not aware of them because the teams involved can be erratic in their performance. However, the Bookie's Over-Round will still generally see that the Bookie will profit overall, no matter how the match result turns out. Your best "hedge" in the case of possible Value Bets is to employ "Double Chance" or "Win Only" betting.