Tiered calculator for wordpress

Hi, I need for a calculator to go onto a website. The calculator is to calculate the price of an organic fertilizer, based on pre packaged amounts. There is 2 types of containers, 25litre bottle, and 1000 liter drum. Amounts need to rounded up to 25 liters if under a total of 1000 liters, and rounded up to the next 1000 once over 1000, eg: 1 order of 500 liters = 20x 25 litre drums. eg: 2 order of 1050 liters =2x 1000 litre drums (not 1x 1000 liters and 2x 25litres. I need exactly this calculator: [login to view URL] and its steps to be incorporated into my own wordpress site via plug in. Plug in need fields to alter the rate of bulk discounts, ie: 25-200 liter - $166, 200+ $1066, 1000+ $4850 and so on for 10,000 liter orders. If a user orders 9200 liters, the price shows at the 10,000 fixed price. See image sample for prices.