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	$174.85	5.551%	$184.5559	$184.56	$184.55	$184.60
Purchase #2	$123.38	8.850%	$134.2991	$134.30	$134.30	$134.30
Purchase #3	$151.81	4.359%	$158.4274	$158.43	$158.45	$158.40
Purchase #4	$80.63	11.569%	$89.9581	$89.96	$89.95	$90.00
Purchase #5	$160.42	6.240%	$170.4302	$170.43	$170.45	$170.40
Purchase #6	$38.72	6.403%	$41.1992	$41.20	$41.20	$41.20
Purchase #7	$165.89	11.235%	$184.5277	$184.53	$184.55	$184.50
7 purchase totals =	$895.70		$963.3976	$963.41	$963.45	$963.40