Editing Orders without Auto Updating

I notice that when I have an order/quote and I have set custom prices, when I get in an edit the order such as change the time, all the amounts and tax rates change to what the system shows. Is there a way to get the orders not to change automatically unless I make specific changes? For example, order 70745, I have it in the system with a tax rate of 9.2% and the item is $150. When I update the system with the a different tax rate and go in to edit the order by changing the time, it changes the tax and it puts the item to $250. I do not want it to do this. Please let me know if you have questions.