Rather than entering the exact purchase amount into your check register, round that amount up.
Example: I purchased something for $34.46; I'd round that up to $35.00 in my register.
The change adds up after a while! Do that for a couple of months to add a cushion to your account, or take that extra and put it into your savings. You're not missing pennies, anyway!
Benefits are saving extra without even trying, protecting your account if you overdraft some day, putting money away for new fitness equipment or clothing -- endless positive things!