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	$234.49	8.717%	$254.9305	$254.93	$254.95	$254.90
Purchase #2	$179.95	11.601%	$200.826	$200.83	$200.85	$200.80
Purchase #3	$99.40	6.437%	$105.7984	$105.80	$105.80	$105.80
Purchase #4	$22.71	6.756%	$24.2443	$24.24	$24.25	$24.20
Purchase #5	$206.88	3.619%	$214.367	$214.37	$214.35	$214.40
Purchase #6	$150.75	13.253%	$170.7289	$170.73	$170.75	$170.70
Purchase #7	$106.44	4.689%	$111.431	$111.43	$111.45	$111.40
7 purchase totals =	$1,000.62		$1,082.3261	$1,082.33	$1,082.40	$1,082.20