Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$41.33	4.333%	$43.1208	$43.12	$43.10	$43.10
Purchase #2	$160.51	7.567%	$172.6558	$172.66	$172.65	$172.70
Purchase #3	$83.71	8.470%	$90.8002	$90.80	$90.80	$90.80
Purchase #4	$181.76	6.382%	$193.3599	$193.36	$193.35	$193.40
Purchase #5	$237.54	6.818%	$253.7355	$253.74	$253.75	$253.70
Purchase #6	$40.68	12.583%	$45.7988	$45.80	$45.80	$45.80
Purchase #7	$43.43	7.572%	$46.7185	$46.72	$46.70	$46.70
7 purchase totals =	$788.96		$846.1895	$846.20	$846.15	$846.20