I think this is useful on some no-annual-fee credit cards which you are planning on keeping forever (but not being used frequently). You can add them to your Amazon account and buy $0.99 e-Gift Card for yourself each month. FYI, the minimum amount allowed is $0.15.
This is also useful to those daily credit cards (if they allow this small balance adjustment). You can pay their balance before the statement date and leave a $0.99 balance on it. This can also help your credit score as it optimize your credit utilization ratio.
The main question now is how many credit cards have this "Small Balance Adjustment" function? I will try a few of my credit cards and update this post in the next month. If you have any related information, please comment below. Thanks.