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	$55.98	7.429%	$60.1388	$60.14	$60.15	$60.10
Purchase #2	$249.88	3.165%	$257.7887	$257.79	$257.80	$257.80
Purchase #3	$189.76	5.644%	$200.4701	$200.47	$200.45	$200.50
Purchase #4	$95.47	5.502%	$100.7228	$100.72	$100.70	$100.70
Purchase #5	$34.89	7.792%	$37.6086	$37.61	$37.60	$37.60
Purchase #6	$47.47	10.255%	$52.338	$52.34	$52.35	$52.30
Purchase #7	$196.86	8.105%	$212.8155	$212.82	$212.80	$212.80
7 purchase totals =	$870.31		$921.8825	$921.89	$921.85	$921.80