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	$22.65	9.630%	$24.8312	$24.83	$24.85	$24.80
Purchase #2	$47.34	6.819%	$50.5681	$50.57	$50.55	$50.60
Purchase #3	$74.49	5.250%	$78.4007	$78.40	$78.40	$78.40
Purchase #4	$59.41	12.589%	$66.8891	$66.89	$66.90	$66.90
Purchase #5	$99.26	11.240%	$110.4168	$110.42	$110.40	$110.40
Purchase #6	$214.55	13.261%	$243.0015	$243.00	$243.00	$243.00
Purchase #7	$54.59	5.564%	$57.6274	$57.63	$57.65	$57.60
7 purchase totals =	$572.29		$631.7348	$631.74	$631.75	$631.70