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	$39.49	8.597%	$42.885	$42.89	$42.90	$42.90
Purchase #2	$227.95	12.182%	$255.7189	$255.72	$255.70	$255.70
Purchase #3	$95.89	6.455%	$102.0797	$102.08	$102.10	$102.10
Purchase #4	$183.80	3.169%	$189.6246	$189.62	$189.60	$189.60
Purchase #5	$174.64	13.224%	$197.7344	$197.73	$197.75	$197.70
Purchase #6	$139.32	6.594%	$148.5068	$148.51	$148.50	$148.50
Purchase #7	$111.54	12.449%	$125.4256	$125.43	$125.45	$125.40
7 purchase totals =	$972.63		$1,061.9750	$1,061.98	$1,062.00	$1,061.90