Script to Reprice Active BIN Ebay Listings by X% (ebay API)

I need a script to reprice all my active UK ebay listings by a % that we input. All our items are Buy It Now fixed prices with 1,3,5,7 or 30 day listings. The script should work like this: We input a fixed percentage that we want to increase/decrease our base prices by (must allow +/-). The active listings will be rounded up (if >= .25 or .75) or rounded down (if <= .25 or .75) to the nearest.49 or .95. If an item has already had its price adjusted once, IT WILL NOT BE ADJUSTED AGAIN. I intend to run the script on a daily cron and don't want the prices to be continuously revised. eg Monday morning - we post a RED CHAIR for £4.95 Monday Evening - we run the script to increase prices by +12%. RED CHAIR price + 12% is £5.54 but gets rounded down to £5.49 Tuesday - post a BLUE CHAIR for £9.95 Tuesday Evening - we run the script to decrease prices by 17%. RED CHAIR price remains the same as the price has already been revised once whilt the item is active. BLUE CHAIR price - 13% is £8.66. This gets rounded up to £8.95 Pm me with your past experience working with the ebay api and, you must be able to complete all of the task.