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	$41.50	11.108%	$46.1098	$46.11	$46.10	$46.10
Purchase #2	$245.94	3.119%	$253.6109	$253.61	$253.60	$253.60
Purchase #3	$52.62	12.765%	$59.3369	$59.34	$59.35	$59.30
Purchase #4	$11.89	6.354%	$12.6455	$12.65	$12.65	$12.60
Purchase #5	$20.88	8.526%	$22.6602	$22.66	$22.65	$22.70
Purchase #6	$157.78	9.407%	$172.6224	$172.62	$172.60	$172.60
Purchase #7	$9.73	6.351%	$10.348	$10.35	$10.35	$10.30
7 purchase totals =	$540.34		$577.3337	$577.34	$577.30	$577.20