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	$154.92	4.186%	$161.405	$161.41	$161.40	$161.40
Purchase #2	$49.39	11.192%	$54.9177	$54.92	$54.90	$54.90
Purchase #3	$98.25	5.773%	$103.922	$103.92	$103.90	$103.90
Purchase #4	$140.58	11.695%	$157.0208	$157.02	$157.00	$157.00
Purchase #5	$105.77	5.120%	$111.1854	$111.19	$111.20	$111.20
Purchase #6	$58.31	6.794%	$62.2716	$62.27	$62.25	$62.30
Purchase #7	$19.71	10.834%	$21.8454	$21.85	$21.85	$21.80
7 purchase totals =	$626.93		$672.5679	$672.58	$672.50	$672.50