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	$214.61	7.652%	$231.032	$231.03	$231.05	$231.00
Purchase #2	$161.75	8.208%	$175.0264	$175.03	$175.05	$175.00
Purchase #3	$45.56	5.770%	$48.1888	$48.19	$48.20	$48.20
Purchase #4	$73.51	13.466%	$83.4089	$83.41	$83.40	$83.40
Purchase #5	$29.78	13.817%	$33.8947	$33.89	$33.90	$33.90
Purchase #6	$209.57	10.229%	$231.0069	$231.01	$231.00	$231.00
Purchase #7	$89.72	6.810%	$95.8299	$95.83	$95.85	$95.80
7 purchase totals =	$824.50		$898.3876	$898.39	$898.45	$898.30