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	$97.90	10.293%	$107.9768	$107.98	$108.00	$108.00
Purchase #2	$42.35	10.119%	$46.6354	$46.64	$46.65	$46.60
Purchase #3	$76.31	8.743%	$82.9818	$82.98	$83.00	$83.00
Purchase #4	$60.88	9.227%	$66.4974	$66.50	$66.50	$66.50
Purchase #5	$55.47	6.533%	$59.0939	$59.09	$59.10	$59.10
Purchase #6	$236.90	12.528%	$266.5788	$266.58	$266.60	$266.60
Purchase #7	$80.56	13.192%	$91.1875	$91.19	$91.20	$91.20
7 purchase totals =	$650.37		$720.9516	$720.96	$721.05	$721.00