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	$176.32	7.630%	$189.7732	$189.77	$189.75	$189.80
Purchase #2	$11.37	11.418%	$12.6682	$12.67	$12.65	$12.70
Purchase #3	$231.61	6.682%	$247.0862	$247.09	$247.10	$247.10
Purchase #4	$86.72	4.422%	$90.5548	$90.55	$90.55	$90.60
Purchase #5	$156.64	10.236%	$172.6737	$172.67	$172.65	$172.70
Purchase #6	$95.46	6.238%	$101.4148	$101.41	$101.40	$101.40
Purchase #7	$56.45	8.650%	$61.3329	$61.33	$61.35	$61.30
7 purchase totals =	$814.57		$875.5038	$875.49	$875.45	$875.60