Discount based on amount?

Hi there,

I am sure there is a clever sole that can help me with the following:

I need to create a price list a we give a discount based on the price of the product for example:

All products over £100 have a 10% Discount, how do this and also at the sametime round the value up to 0.99p

ie Product ZXY123 is £123.99 10% off is £111.59 we need the calculated price to be £111.99

Anyone know please, this would save me loads of time as we have 1000's of prices.

Thanks in advance

Sean