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	$58.42	5.531%	$61.6512	$61.65	$61.65	$61.70
Purchase #2	$59.65	12.217%	$66.9374	$66.94	$66.95	$66.90
Purchase #3	$106.79	4.782%	$111.8967	$111.90	$111.90	$111.90
Purchase #4	$11.99	3.682%	$12.4315	$12.43	$12.45	$12.40
Purchase #5	$136.89	13.694%	$155.6357	$155.64	$155.65	$155.60
Purchase #6	$54.41	11.846%	$60.8554	$60.86	$60.85	$60.90
Purchase #7	$218.79	12.493%	$246.1234	$246.12	$246.10	$246.10
7 purchase totals =	$646.94		$715.5313	$715.54	$715.55	$715.50