excise duty in export under Rebate claim process

Hi,

I have mapped export sale under rebate claim.

In billing, the excise duty coming as 12.36 usd = 681.65 inr

But in excise invoice,the excise duty getting rounding off which is 13 usd= 682 inr

for which the rebate claim a/c will not knock off.

Please help me how to treat this excise duty.

Thanks.