Please recommend me a suitable shopping cart plugin to meet my requirements

Hi.

I’ve been trying out several shopping cart plugins, but i could not find one which can handle what i want to do.
I hope somebody could tell me if there is any shopping cart plugin which meets my requirement.

I’m trying to sell something and the fee calculation is as follows.
Total = (Item price + Transaction fee) x 1.05

Transaction fee differs from item price.
For example,
item fr $1-$100 : transaction fee of $10
item fr $101-$500 : transaction fee of $50
item fr $501 onwards : transaction fee of 10% of total amount

So, let’s say i am selling an item of $300.
The total amount that the buyer should pay me is
Total = (300 + 50) x 1.05

I’ve tried out “WP Paypal Shopping Cart”.
Since it does not have any option to set on the transaction fee,
I use the shipping calculation in my paypal settings to do it.
Unfortunately, I can choose “flat fee” or “%” for my calculation, which means mix case like the following is not allowed.
item fr $1-$100 : transaction fee of $10 <–FLAT FEE
item fr $101-$500 : transaction fee of $50 <– FLAT FEE
item fr $501 onwards : transaction fee of 10% of total amount <– PERCENTAGE

Furthermore, I cant add up a 5% of tax to the total calculation.

Is there anyone who can recommend me any cart plugin which is able to set up a fee based on total amount?

Thank you.