Discount in Pricing condition type

Hi,

We have a scenario in which we have a discount condition type K005(Customer/Material discount).

We have maintained the scales as

if the order qty is 1-99 qty then 5% discount

if the order qty is 100-499 qty then 10% discount

if the order qty is 500-1000 and above qty then 15% discount

Now business has a new requirement that if the customer places an order of 80 qty then he will get the discount as 5%.

And when Again the same customer places the order of suppose 50 qty now the discount would be 10% because the total order qty of that customer would be 130 and further same as.

Kindly suggest how to map this scenario in the SAP system.

Thanks & Regards

Ritesh Kumar