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	$67.81	4.768%	$71.0432	$71.04	$71.05	$71.00
Purchase #2	$97.50	9.222%	$106.4915	$106.49	$106.50	$106.50
Purchase #3	$154.75	6.251%	$164.4234	$164.42	$164.40	$164.40
Purchase #4	$63.86	12.419%	$71.7908	$71.79	$71.80	$71.80
Purchase #5	$226.43	12.724%	$255.241	$255.24	$255.25	$255.20
Purchase #6	$232.53	3.699%	$241.1313	$241.13	$241.15	$241.10
Purchase #7	$140.76	7.838%	$151.7928	$151.79	$151.80	$151.80
7 purchase totals =	$983.64		$1,061.9140	$1,061.90	$1,061.95	$1,061.80