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	$13.95	11.450%	$15.5473	$15.55	$15.55	$15.50
Purchase #2	$240.55	7.353%	$258.2376	$258.24	$258.25	$258.20
Purchase #3	$216.69	3.163%	$223.5439	$223.54	$223.55	$223.50
Purchase #4	$37.70	10.399%	$41.6204	$41.62	$41.60	$41.60
Purchase #5	$127.60	13.523%	$144.8553	$144.86	$144.85	$144.90
Purchase #6	$203.59	6.509%	$216.8417	$216.84	$216.85	$216.80
Purchase #7	$173.81	13.603%	$197.4534	$197.45	$197.45	$197.50
7 purchase totals =	$1,013.89		$1,098.0996	$1,098.10	$1,098.10	$1,098.00