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	$182.40	4.526%	$190.6554	$190.66	$190.65	$190.70
Purchase #2	$122.65	6.307%	$130.3855	$130.39	$130.40	$130.40
Purchase #3	$41.94	9.131%	$45.7695	$45.77	$45.75	$45.80
Purchase #4	$124.95	13.585%	$141.9245	$141.92	$141.90	$141.90
Purchase #5	$146.88	12.149%	$164.7245	$164.72	$164.70	$164.70
Purchase #6	$151.25	3.440%	$156.453	$156.45	$156.45	$156.50
Purchase #7	$61.46	7.450%	$66.0388	$66.04	$66.05	$66.00
7 purchase totals =	$831.53		$895.9512	$895.95	$895.90	$896.00