Does every single purchase/item need to be listed as its own entry when listing business expenses, or can related purchases/items be grouped as a single entry?

[rjs]

Just enter the total for each type of expense. Do not list each individual purchase. But you should keep the detailed information with your tax records to show how you arrived at the totals, in case you get audited.

[JamesG1]

Self-employment expenditures should be grouped into the categories that the IRS lists on IRS Form 1040 Schedule C.

Other expenses that do not fit in these categories are listed in Part V Other Expenses.

See also this IRS publication.