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	$41.49	10.116%	$45.6871	$45.69	$45.70	$45.70
Purchase #2	$70.88	10.179%	$78.0949	$78.09	$78.10	$78.10
Purchase #3	$34.44	11.839%	$38.5174	$38.52	$38.50	$38.50
Purchase #4	$250.61	7.580%	$269.6062	$269.61	$269.60	$269.60
Purchase #5	$119.81	5.828%	$126.7925	$126.79	$126.80	$126.80
Purchase #6	$117.78	12.864%	$132.9312	$132.93	$132.95	$132.90
Purchase #7	$227.60	9.136%	$248.3935	$248.39	$248.40	$248.40
7 purchase totals =	$862.61		$940.0228	$940.02	$940.05	$940.00