I have two currencies on the website: CAD and USD. The main is CAD. When we enter the prices in CAD, the site automatically recalculates to the US if the visitors are from US IP, but that number often times is weird, like $132.23. How can I turn the calculation off and enter a manual number, in this example case, I would enter: $130 or $135.
You won't be able to specify a conversion for particular products, but you could automatically round the price to the nearest increment of $5 with a few changes to the currency conversion code. I would strongly recommend against this though as you would then be displaying an incorrect price to the user.
I recently put a change in for another client where they display the converted price without the cents, and with an 'approximate' signifier e.g. 'Approx $132 USD'. Perhaps you could try something like this? If you're using the standard currency converter I can post the code in here and give you instructions on how to implement it, if you're using an app you'll need to contact the app developer.