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	$43.72	11.418%	$48.7119	$48.71	$48.70	$48.70
Purchase #2	$18.75	3.565%	$19.4184	$19.42	$19.40	$19.40
Purchase #3	$100.40	10.573%	$111.0153	$111.02	$111.00	$111.00
Purchase #4	$155.36	3.121%	$160.2088	$160.21	$160.20	$160.20
Purchase #5	$61.38	11.359%	$68.3522	$68.35	$68.35	$68.40
Purchase #6	$166.95	10.733%	$184.8687	$184.87	$184.85	$184.90
Purchase #7	$36.29	11.371%	$40.4165	$40.42	$40.40	$40.40
7 purchase totals =	$582.85		$632.9918	$633.00	$632.90	$633.00