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	$10.39	11.807%	$11.6167	$11.62	$11.60	$11.60
Purchase #2	$145.95	3.778%	$151.464	$151.46	$151.45	$151.50
Purchase #3	$152.51	9.107%	$166.3991	$166.40	$166.40	$166.40
Purchase #4	$170.54	12.259%	$191.4465	$191.45	$191.45	$191.40
Purchase #5	$48.38	4.229%	$50.426	$50.43	$50.45	$50.40
Purchase #6	$208.48	4.313%	$217.4717	$217.47	$217.45	$217.50
Purchase #7	$126.45	4.265%	$131.8431	$131.84	$131.85	$131.80
7 purchase totals =	$862.70		$920.6671	$920.67	$920.65	$920.60