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	$166.87	10.462%	$184.3279	$184.33	$184.35	$184.30
Purchase #2	$167.35	13.838%	$190.5079	$190.51	$190.50	$190.50
Purchase #3	$32.44	6.739%	$34.6261	$34.63	$34.65	$34.60
Purchase #4	$63.41	3.450%	$65.5976	$65.60	$65.60	$65.60
Purchase #5	$241.45	10.716%	$267.3238	$267.32	$267.30	$267.30
Purchase #6	$141.44	7.182%	$151.5982	$151.60	$151.60	$151.60
Purchase #7	$59.94	8.654%	$65.1272	$65.13	$65.15	$65.10
7 purchase totals =	$872.90		$959.1087	$959.12	$959.15	$959.00