You could do that with some custom coding here, but keep in mind that once the products are at checkout, they will revert back to the original currency. Let us know what you're trying to achieve here.
That is what I am running into. I am able to change the formatting of the "price" to remove the decimals and replace USD with "Points", however in the checkout it still shows as $. I am creating a site for my client where the user will not pay for the product but he wants to show a value for each item in points. Each user would be told they have 5 points to "spend", the checkout would show a manual payment method to allow them to checkout without a credit card. We would monitor the point totals after the order was placed to ensure someone did not "overspend". Hopefully that make sense.