I am trying to create a formula for my consignment business and I am having a
little trouble. Here is what I need the formula to do:

If item sells for 300 or less 25% times the sales price,

If item sells for300.01- 500, 25% of first 300 + 20% of the remaining amount
betweem 300.01-500.

If it sells for 500.01-1000, 25% of first 300, +20% of 300.01-500,+ 15%the
remaining amount between 500.01-1000.

If item sells for 1000 or more, 25% of first 300, +20% of 300.01-500, +15%
of 500.01-1000, + 10% of the remaining amount over $1,000.

ex. I sell a $750 guitar at my store

I recieve 25% of first $300= $75
20% of 300.01-500= $40
15% of 500.01-750=$37.5
Total Commission= $152.5

I enter the following formula:
IF(E22<300,SUM(E22)*25%,SUM((E22-300)*20%+75))

This formula allows me to solve the total commission for items under $300,
and Items over $300, however, I can only assign 20% commission to items over
$300. How can I create multiple rules for a single cell?