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	$187.45	8.597%	$203.5651	$203.57	$203.55	$203.60
Purchase #2	$140.42	11.376%	$156.3942	$156.39	$156.40	$156.40
Purchase #3	$186.51	11.858%	$208.6264	$208.63	$208.65	$208.60
Purchase #4	$59.89	11.733%	$66.9169	$66.92	$66.90	$66.90
Purchase #5	$217.88	5.144%	$229.0877	$229.09	$229.10	$229.10
Purchase #6	$146.84	3.788%	$152.4023	$152.40	$152.40	$152.40
Purchase #7	$89.49	11.172%	$99.4878	$99.49	$99.50	$99.50
7 purchase totals =	$1,028.48		$1,116.4804	$1,116.49	$1,116.50	$1,116.50