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	$97.56	11.406%	$108.6877	$108.69	$108.70	$108.70
Purchase #2	$88.88	12.733%	$100.1971	$100.20	$100.20	$100.20
Purchase #3	$181.83	4.413%	$189.8542	$189.85	$189.85	$189.90
Purchase #4	$114.96	4.715%	$120.3804	$120.38	$120.40	$120.40
Purchase #5	$50.43	7.203%	$54.0625	$54.06	$54.05	$54.10
Purchase #6	$24.38	12.456%	$27.4168	$27.42	$27.40	$27.40
Purchase #7	$230.56	5.583%	$243.4322	$243.43	$243.45	$243.40
7 purchase totals =	$788.60		$844.0309	$844.03	$844.05	$844.10