The rewards were in full dollars, rounded.
So, you spend $50.01 - get $1.00
Spend $75 - get $1.00
Spend $100 - get $1.00
Spend $128 - get $1.00
Spend $149.99 - get $1.00
Now, they won't be rounding to full dollars.
Spend $50.01 - get 50 cents
Spend $75 - get 75 cents
Spend $100 - get $1.00
Spend $128 - get $1.28
Spend $149.99 - get $1.50
The example they gave with the $128 is where you would earn 28 extra cents. If you spend $178 - you lose 22 cents in the new system.
So, some months you get a few more cents, other months you lose a few cents. In the end, probably comes out even.