I have used checkout_cart_product_add_after event, for change product price.
Used observer code like below
$item->setCustomPrice($price); $item->setOriginalCustomPrice($price); $item->getProduct()->setIsSuperMode(true);
Above code is not working while multi-currency, On cart page, if I added the product with price 100$ it is showing $100.
When I am changing currency from the switcher to INR, It was showing ₹100.
If I disabled event and add to cart same product, it's working properly in both currencies.