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	$52.71	13.636%	$59.8975	$59.90	$59.90	$59.90
Purchase #2	$21.26	13.470%	$24.1237	$24.12	$24.10	$24.10
Purchase #3	$32.27	5.634%	$34.0881	$34.09	$34.10	$34.10
Purchase #4	$133.97	5.395%	$141.1977	$141.20	$141.20	$141.20
Purchase #5	$65.73	8.604%	$71.3854	$71.39	$71.40	$71.40
Purchase #6	$59.79	8.243%	$64.7185	$64.72	$64.70	$64.70
Purchase #7	$146.73	3.536%	$151.9184	$151.92	$151.90	$151.90
7 purchase totals =	$512.46		$547.3293	$547.34	$547.30	$547.30