The bulk sale invoice would just be an invoice usually with one line, unless you have various VAT rates in use.
You could import these as separate invoices if you wish from a CSV file (e.g. daily or weekly sales imported on a monthly basis). You could even attach a copy of the backing data to the invoice itself so it’s easy to trace once the invoice has been created.
We have two articles around the basis of bulk logging sales which may be of interest: