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	$141.25	13.729%	$160.6422	$160.64	$160.65	$160.60
Purchase #2	$115.84	8.866%	$126.1104	$126.11	$126.10	$126.10
Purchase #3	$55.90	6.592%	$59.5849	$59.58	$59.60	$59.60
Purchase #4	$177.47	10.536%	$196.1682	$196.17	$196.15	$196.20
Purchase #5	$11.85	4.332%	$12.3633	$12.36	$12.35	$12.40
Purchase #6	$88.55	4.355%	$92.4064	$92.41	$92.40	$92.40
Purchase #7	$99.88	8.589%	$108.4587	$108.46	$108.45	$108.50
7 purchase totals =	$690.74		$755.7341	$755.73	$755.70	$755.80