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	$53.70	5.581%	$56.697	$56.70	$56.70	$56.70
Purchase #2	$40.44	7.326%	$43.4026	$43.40	$43.40	$43.40
Purchase #3	$114.63	7.727%	$123.4875	$123.49	$123.50	$123.50
Purchase #4	$101.44	4.583%	$106.089	$106.09	$106.10	$106.10
Purchase #5	$243.58	10.530%	$269.229	$269.23	$269.25	$269.20
Purchase #6	$144.82	11.516%	$161.4975	$161.50	$161.50	$161.50
Purchase #7	$123.64	11.288%	$137.5965	$137.60	$137.60	$137.60
7 purchase totals =	$822.25		$897.9991	$898.01	$898.05	$898.00