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	$49.67	6.351%	$52.8245	$52.82	$52.80	$52.80
Purchase #2	$184.81	12.792%	$208.4509	$208.45	$208.45	$208.50
Purchase #3	$33.58	13.679%	$38.1734	$38.17	$38.15	$38.20
Purchase #4	$93.49	7.640%	$100.6326	$100.63	$100.65	$100.60
Purchase #5	$244.76	10.550%	$270.5822	$270.58	$270.60	$270.60
Purchase #6	$45.56	5.111%	$47.8886	$47.89	$47.90	$47.90
Purchase #7	$198.27	8.549%	$215.2201	$215.22	$215.20	$215.20
7 purchase totals =	$850.14		$933.7723	$933.76	$933.75	$933.80