Discount on the product?

Discount on the product?

I have multidimensional array:
$products = array(
array(
'id' => 'sku_123ABC',
'qty' => 1,
'price' => 39.95,
'name' => 'T-Shirt',
),
array(
'id' => 'sku_567ZYX',
'qty' => 1,
'price' => 9.95,
'name' => 'Coffee Mug'
),
array(
'id' => 'sku_965QRS',
'qty' => 1,
'price' => 29.95,
'name' => 'Shot Glass'
)
);
I know how to count total price of products, but what i need is discount,
to look like this way
Any 2 products 10% discount
Any 3 products 20% discount
5 + products 30%discount
The problem I have is that i know how to count numbers of array members,
and i have qty i know that too, but i know how to do that ony counting by
qty or array members? Is theere some solution to apply this discounts on
$products array and display total price