An item's sales price that shows in the item list is the default price that is automatically brought into an invoice, sales order or credit memo and is used for the Sales/Accounts Receivable calculations.
If you do not want QuickBooks to use more than two decimal places in the sales calculations, you can:
NOTE: You cannot change the number of decimal places used in the Inventory/COGS calculation.
Manually change the rate for an item to the desired rate on the invoice. This will not affect the sales price in the item list.
NOTE: This change does not affect any previous transactions, but will affect all future ones.