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	$101.62	9.670%	$111.4467	$111.45	$111.45	$111.40
Purchase #2	$59.88	11.715%	$66.8949	$66.89	$66.90	$66.90
Purchase #3	$229.42	5.736%	$242.5795	$242.58	$242.60	$242.60
Purchase #4	$115.43	8.229%	$124.9287	$124.93	$124.95	$124.90
Purchase #5	$240.54	4.256%	$250.7774	$250.78	$250.80	$250.80
Purchase #6	$74.35	6.167%	$78.9352	$78.94	$78.95	$78.90
Purchase #7	$11.84	11.415%	$13.1915	$13.19	$13.20	$13.20
7 purchase totals =	$833.08		$888.7539	$888.76	$888.85	$888.70