Hi,
Are you using the option "send order details" in your Paypal plugin configuration ? If so, please disable it.
This option can introduce price average problem because HikaShop have more precise prices for the products, that Paypal won't use (paypal just use two digits).
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.