You can define a general ledger account for rounding differences through transaction cod OB00 or by using the following path;
SPRO > Financial Accounting > Accounts Receivable and Accounts Payable > Business Transactions > Outgoing Payments > Outgoing Payments Global Settings > Define Account for Rounding Differences
You need to create your general ledger account before assigning the same here. This configuration will work for both the vendor and customer account
Just enter your Chart of accounts in the initial screen and then enter the general ledger account under the option account.
Save it to define the accounts for rounding differences
Define accounts for Bank Charges (Vendor)
You can define accounts for bank charges by using transaction code OBXK
SPRO > Financial Accounting > Accounts Receivable and Accounts Payable > Business Transactions > Outgoing Payments > Outgoing Payments Global Settings > Define Account for Bank Charges (Vendor)
Double click on the Transaction BSP and enter the general ledger account you created for the account posting. Save it to define the accounts for bank charges (vendor).
This configuration will work for both the vendor and customer but you must create the bank account as relevant for cash flow while creating it through transaction code FS00.