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	$74.72	10.169%	$82.3183	$82.32	$82.30	$82.30
Purchase #2	$226.94	12.584%	$255.4981	$255.50	$255.50	$255.50
Purchase #3	$10.71	9.438%	$11.7208	$11.72	$11.70	$11.70
Purchase #4	$226.47	9.813%	$248.6935	$248.69	$248.70	$248.70
Purchase #5	$179.56	11.472%	$200.1591	$200.16	$200.15	$200.20
Purchase #6	$94.38	5.653%	$99.7153	$99.72	$99.70	$99.70
Purchase #7	$99.49	8.719%	$108.1645	$108.16	$108.15	$108.20
7 purchase totals =	$912.27		$1,006.2696	$1,006.27	$1,006.20	$1,006.30