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	$104.31	11.116%	$115.9051	$115.91	$115.90	$115.90
Purchase #2	$171.52	7.335%	$184.101	$184.10	$184.10	$184.10
Purchase #3	$140.27	11.682%	$156.6563	$156.66	$156.65	$156.70
Purchase #4	$40.85	8.733%	$44.4174	$44.42	$44.40	$44.40
Purchase #5	$93.50	4.270%	$97.4925	$97.49	$97.50	$97.50
Purchase #6	$105.31	5.718%	$111.3316	$111.33	$111.35	$111.30
Purchase #7	$245.70	10.539%	$271.5943	$271.59	$271.60	$271.60
7 purchase totals =	$901.46		$981.4982	$981.50	$981.50	$981.50