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	$217.47	5.733%	$229.9376	$229.94	$229.95	$229.90
Purchase #2	$21.88	11.266%	$24.345	$24.35	$24.35	$24.30
Purchase #3	$77.66	11.566%	$86.6422	$86.64	$86.65	$86.60
Purchase #4	$33.72	10.493%	$37.2582	$37.26	$37.25	$37.30
Purchase #5	$54.41	10.389%	$60.0627	$60.06	$60.05	$60.10
Purchase #6	$133.40	9.102%	$145.5421	$145.54	$145.55	$145.50
Purchase #7	$63.74	5.249%	$67.0857	$67.09	$67.10	$67.10
7 purchase totals =	$602.28		$650.8735	$650.88	$650.90	$650.80