How to simplify complicated business "IF" logic?

What are the good ways to handle complicated business logic that from the first glance requires many nested if statements?

Example:

Discount Coupon. could be:

1a) Value discount
1b) Percentage discount

2a) Normal discount
2b) Progressive discount

3a) Requires access coupon
3b) Do not require access coupon

4a) Applied only to the customer who already bought before
4b) Applied to any customer

5a) Applied to customer only from countries (X,Y,…)

That requires code even more complicated then this:

if (discount.isPercentage) {
    if (discount.isNormal) {
        if (discount.requiresAccessCoupon) {
        } else {
        }
    } else if (discount.isProgressive) {
        if (discount.requiresAccessCoupon) {
        } else {
        }
    }
} else if (discount.isValue) {
    if (discount.isNormal) {
        if (discount.requiresAccessCoupon) {
        } else {
        }
    } else if (discount.isProgressive) {
        if (discount.requiresAccessCoupon) {
        } else {
        }
    }
} else if (discount.isXXX) {
    if (discount.isNormal) {
    } else if (discount.isProgressive) {
    }
}

Even if you replace IFs to switch/case it's still too complicated. What are the ways to make it readable, maintainable, more testable and easy to understand?

I would write a generic state-machine that feeds on lists of things to compare.