Commerce Quantity Volume Discount Rules
Figured it out. Here's the rules settings. This will take 10% off your order if the total quantity of your cart is 14+

{ "rules_overall_discount" : {
    "LABEL" : "Volume Discount",
    "PLUGIN" : "reaction rule",
    "OWNER" : "rules",
    "REQUIRES" : [ "commerce_order", "commerce_line_item", "commerce_product_reference" ],
    "ON" : { "commerce_product_calculate_sell_price" : [] },
    "IF" : [
      { "commerce_order_compare_total_product_quantity" : {
          "commerce_order" : [ "site:current-cart-order" ],
          "operator" : "\u003E=",
          "value" : "14"
        }
      }
    ],
    "DO" : [
      { "commerce_line_item_unit_price_multiply" : {
          "commerce_line_item" : [ "commerce_line_item" ],
          "amount" : ".9",
          "component_name" : "base_price",
          "round_mode" : "1"
        }
      }
    ]
  }
}