Totals by category
  Groceries         $16.50
  Office Supplies   $8.00
  Hardware          $13.00

Totals by receipt
  receipt-01.txt  2025-05-05  Pebble Pantry       $10.00  (printed subtotal $10.00, total $10.00)
  receipt-02.txt  2025-05-06  Lantern Stationery  $8.00  (printed subtotal $8.00, total $8.00)
  receipt-03.txt  2025-05-07  Pebble Pantry       $6.50  (printed subtotal $6.50, total $6.50)
  receipt-04.txt  2025-05-08  Beacon Hardware     $13.00  (printed subtotal $13.00, total $13.00)

Grand total: $37.50

Mismatches with printed subtotals/totals
  None - every receipt's item sum matches its printed subtotal and total.

Notes: no tax or fee lines appear on these receipts (each states no sales tax).
Categories are assigned by store type: Groceries, Office Supplies, Hardware.
All arithmetic uses Python decimal.Decimal.