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	$57.31	8.503%	$62.1831	$62.18	$62.20	$62.20
Purchase #2	$120.43	5.529%	$127.0886	$127.09	$127.10	$127.10
Purchase #3	$122.87	9.409%	$134.4308	$134.43	$134.45	$134.40
Purchase #4	$105.59	12.845%	$119.153	$119.15	$119.15	$119.20
Purchase #5	$117.25	9.313%	$128.1695	$128.17	$128.15	$128.20
Purchase #6	$41.45	13.277%	$46.9533	$46.95	$46.95	$47.00
Purchase #7	$108.42	4.769%	$113.5905	$113.59	$113.60	$113.60
7 purchase totals =	$673.32		$731.5688	$731.56	$731.60	$731.70