You might consider setting up different adgroups for each plural and word-combination variant. You will often find that you can reduce your bids on many of the keywords combinations, because the competition and CPC will be lower.
Also, this allows you to more precisely target the text in your ads.
Jim
Advertiser 1: 5% ctr, $5 max CPC = bid rank 25
Advertiser 2: 10% CTR, $2 max CPC = bid rank 20
Advertiser 1 needs a bid rank of 21 to be in position 1, so the paid cpc would be 4.01 (4.01 x 5 = 20.05), $0.01 above what they need to be to have a 1pt higher bid rank than the next lower advertiser.
So, it's not 1 cent above. It's 1 point above and that could mean much more than 1 cent. Right?
Actually, no.
...it's 1 pt above the next bid rank number, but the adjustment is made in the paid CPC to determine that number.
Nearly correct, but not quite. It is more likely to be a fraction of a point.
Esentially, the system will put you just above your nearest competitor (in terms of rank number) for the lowest possible CPC increase. And since there is no denomination less than a penny (for USD at any rate), that is what is used.
AWA