Here’re what you need:
100% means 1 point per dollar spent. Spend $100 to get 100 points.
Set the exchange rate to 0.05 means 100 points worth $5 when redeeming.
Alternatively, you can set 500% as the ratio and 0.01 as the exchange rate.
In payment windows, select the POINTS as payment type, hit the INSERT key, the system will automatically calculate how many points need to pay.