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	$70.29	8.777%	$76.4594	$76.46	$76.45	$76.50
Purchase #2	$80.67	6.336%	$85.7813	$85.78	$85.80	$85.80
Purchase #3	$230.94	10.872%	$256.0478	$256.05	$256.05	$256.00
Purchase #4	$236.35	7.257%	$253.5019	$253.50	$253.50	$253.50
Purchase #5	$95.42	10.164%	$105.1185	$105.12	$105.10	$105.10
Purchase #6	$243.42	4.309%	$253.909	$253.91	$253.90	$253.90
Purchase #7	$95.78	5.397%	$100.9492	$100.95	$100.95	$100.90
7 purchase totals =	$1,052.87		$1,131.7671	$1,131.77	$1,131.75	$1,131.70