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	$100.89	10.206%	$111.1868	$111.19	$111.20	$111.20
Purchase #2	$87.77	6.815%	$93.7515	$93.75	$93.75	$93.80
Purchase #3	$221.80	13.106%	$250.8691	$250.87	$250.85	$250.90
Purchase #4	$221.40	12.227%	$248.4706	$248.47	$248.45	$248.50
Purchase #5	$230.98	9.321%	$252.5096	$252.51	$252.50	$252.50
Purchase #6	$17.80	5.575%	$18.7924	$18.79	$18.80	$18.80
Purchase #7	$100.54	8.308%	$108.8929	$108.89	$108.90	$108.90
7 purchase totals =	$981.18		$1,084.4729	$1,084.47	$1,084.45	$1,084.60