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	$232.95	10.247%	$256.8204	$256.82	$256.80	$256.80
Purchase #2	$129.34	10.762%	$143.2596	$143.26	$143.25	$143.30
Purchase #3	$33.95	11.519%	$37.8607	$37.86	$37.85	$37.90
Purchase #4	$237.84	3.766%	$246.7971	$246.80	$246.80	$246.80
Purchase #5	$74.66	5.188%	$78.5334	$78.53	$78.55	$78.50
Purchase #6	$245.64	10.534%	$271.5157	$271.52	$271.50	$271.50
Purchase #7	$44.33	11.754%	$49.5405	$49.54	$49.55	$49.50
7 purchase totals =	$998.71		$1,084.3274	$1,084.33	$1,084.30	$1,084.30