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	$60.82	8.725%	$66.1265	$66.13	$66.15	$66.10
Purchase #2	$165.59	12.721%	$186.6547	$186.65	$186.65	$186.70
Purchase #3	$84.93	7.482%	$91.2845	$91.28	$91.30	$91.30
Purchase #4	$74.60	5.347%	$78.5889	$78.59	$78.60	$78.60
Purchase #5	$87.47	5.754%	$92.503	$92.50	$92.50	$92.50
Purchase #6	$190.86	6.602%	$203.4606	$203.46	$203.45	$203.50
Purchase #7	$10.31	9.874%	$11.328	$11.33	$11.35	$11.30
7 purchase totals =	$674.58		$729.9462	$729.94	$730.00	$730.00