I've did some tests and I think I have a solution to what you need.
Edit your BYR currency via the menu System>Currencies and change the local and international fractional digits options to -1 or -2 or -3 based on the precision of the rounding you want and in the administrator/components/com_hikashop/classes/currency.php, change the code:
Code:
$num = sprintf("%0.{$decimals}f",round($number,$decimals));
to:
Code:
if($decimals<0){
$round = 0;
}else{
$round = $decimals;
}
$num = sprintf("%0.{$round}f",round($number,$decimals));
That should do what you need hopefully.
