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	$153.87	7.132%	$164.844	$164.84	$164.85	$164.80
Purchase #2	$110.75	10.322%	$122.1816	$122.18	$122.20	$122.20
Purchase #3	$57.42	9.563%	$62.9111	$62.91	$62.90	$62.90
Purchase #4	$88.89	11.412%	$99.0341	$99.03	$99.05	$99.00
Purchase #5	$231.48	9.496%	$253.4613	$253.46	$253.45	$253.50
Purchase #6	$100.80	10.813%	$111.6995	$111.70	$111.70	$111.70
Purchase #7	$194.43	5.536%	$205.1936	$205.19	$205.20	$205.20
7 purchase totals =	$937.64		$1,019.3252	$1,019.31	$1,019.35	$1,019.30