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	$99.43	11.780%	$111.1429	$111.14	$111.15	$111.10
Purchase #2	$220.31	11.262%	$245.1213	$245.12	$245.10	$245.10
Purchase #3	$112.30	10.678%	$124.2914	$124.29	$124.30	$124.30
Purchase #4	$117.88	10.248%	$129.9603	$129.96	$129.95	$130.00
Purchase #5	$130.37	4.370%	$136.0672	$136.07	$136.05	$136.10
Purchase #6	$54.81	8.638%	$59.5445	$59.54	$59.55	$59.50
Purchase #7	$80.82	9.346%	$88.3734	$88.37	$88.35	$88.40
7 purchase totals =	$815.92		$894.5010	$894.49	$894.45	$894.50