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	$156.57	5.860%	$165.745	$165.75	$165.75	$165.70
Purchase #2	$88.79	13.356%	$100.6488	$100.65	$100.65	$100.60
Purchase #3	$101.89	4.490%	$106.4649	$106.46	$106.45	$106.50
Purchase #4	$43.55	11.610%	$48.6062	$48.61	$48.60	$48.60
Purchase #5	$153.59	3.140%	$158.4127	$158.41	$158.40	$158.40
Purchase #6	$248.34	3.173%	$256.2198	$256.22	$256.20	$256.20
Purchase #7	$85.70	11.795%	$95.8083	$95.81	$95.80	$95.80
7 purchase totals =	$878.43		$931.9057	$931.91	$931.85	$931.80