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	$56.33	5.871%	$59.6371	$59.64	$59.65	$59.60
Purchase #2	$45.75	3.562%	$47.3796	$47.38	$47.40	$47.40
Purchase #3	$50.66	3.476%	$52.4209	$52.42	$52.40	$52.40
Purchase #4	$9.71	8.491%	$10.5345	$10.53	$10.55	$10.50
Purchase #5	$83.64	10.874%	$92.735	$92.74	$92.75	$92.70
Purchase #6	$104.94	6.555%	$111.8188	$111.82	$111.80	$111.80
Purchase #7	$132.96	7.323%	$142.6967	$142.70	$142.70	$142.70
7 purchase totals =	$483.99		$517.2226	$517.23	$517.25	$517.10