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	$105.64	10.413%	$116.6403	$116.64	$116.65	$116.60
Purchase #2	$103.81	8.452%	$112.584	$112.58	$112.60	$112.60
Purchase #3	$74.72	4.725%	$78.2505	$78.25	$78.25	$78.30
Purchase #4	$127.69	12.546%	$143.71	$143.71	$143.70	$143.70
Purchase #5	$203.26	10.130%	$223.8502	$223.85	$223.85	$223.90
Purchase #6	$230.58	4.801%	$241.6501	$241.65	$241.65	$241.70
Purchase #7	$34.94	10.256%	$38.5234	$38.52	$38.50	$38.50
7 purchase totals =	$880.64		$955.2085	$955.20	$955.20	$955.30