Role Based Pricing for WooCommerce

Currently, the plugin features a min/max quantity rule to give discounts to specific roles. What would be great is if there were added functionality to have different tiers of discounts based on the order subtotal. For example: subtotal = $100 – $199 gets 10% off. subtotal = $200+ gets 15% off. This is not based on the quantity of any specific item but the cumulative subtotal of all items.