in vending.c
rewrite
pc_payzeny(sd, (int)z, LOG_TYPE_VENDING, vsd);
if( battle_config.vending_tax )
z -= z * (battle_config.vending_tax/10000.);
pc_getzeny(vsd, (int)z, LOG_TYPE_VENDING, sd);
to
else
{
pc_payzeny(sd, (int)z, LOG_TYPE_VENDING, vsd);
if( battle_config.vending_tax )
z -= z * (battle_config.vending_tax/10000.);
pc_getzeny(vsd, (int)z, LOG_TYPE_VENDING, sd);
}