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	$89.49	4.546%	$93.5582	$93.56	$93.55	$93.60
Purchase #2	$111.81	5.373%	$117.8176	$117.82	$117.80	$117.80
Purchase #3	$120.83	4.658%	$126.4583	$126.46	$126.45	$126.50
Purchase #4	$153.35	5.233%	$161.3748	$161.37	$161.35	$161.40
Purchase #5	$212.31	9.176%	$231.7916	$231.79	$231.80	$231.80
Purchase #6	$81.55	11.335%	$90.7937	$90.79	$90.80	$90.80
Purchase #7	$136.78	7.105%	$146.4982	$146.50	$146.50	$146.50
7 purchase totals =	$906.12		$968.2924	$968.29	$968.25	$968.40