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	$228.60	11.487%	$254.8593	$254.86	$254.85	$254.90
Purchase #2	$166.97	5.774%	$176.6108	$176.61	$176.60	$176.60
Purchase #3	$176.72	13.643%	$200.8299	$200.83	$200.85	$200.80
Purchase #4	$208.47	12.426%	$234.3745	$234.37	$234.35	$234.40
Purchase #5	$100.35	13.310%	$113.7066	$113.71	$113.70	$113.70
Purchase #6	$82.40	10.492%	$91.0454	$91.05	$91.05	$91.00
Purchase #7	$155.78	13.301%	$176.5003	$176.50	$176.50	$176.50
7 purchase totals =	$1,119.29		$1,247.9268	$1,247.93	$1,247.90	$1,247.90