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	$89.53	7.817%	$96.5286	$96.53	$96.55	$96.50
Purchase #2	$40.83	10.595%	$45.1559	$45.16	$45.15	$45.20
Purchase #3	$130.99	11.152%	$145.598	$145.60	$145.60	$145.60
Purchase #4	$56.26	5.514%	$59.3622	$59.36	$59.35	$59.40
Purchase #5	$30.59	12.536%	$34.4248	$34.42	$34.40	$34.40
Purchase #6	$23.34	3.231%	$24.0941	$24.09	$24.10	$24.10
Purchase #7	$18.67	4.778%	$19.5621	$19.56	$19.55	$19.60
7 purchase totals =	$390.21		$424.7257	$424.72	$424.70	$424.80