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	$230.79	10.773%	$255.653	$255.65	$255.65	$255.70
Purchase #2	$103.83	8.189%	$112.3326	$112.33	$112.35	$112.30
Purchase #3	$75.65	11.854%	$84.6176	$84.62	$84.60	$84.60
Purchase #4	$206.32	7.385%	$221.5567	$221.56	$221.55	$221.60
Purchase #5	$87.76	13.834%	$99.9007	$99.90	$99.90	$99.90
Purchase #6	$223.38	7.809%	$240.8237	$240.82	$240.80	$240.80
Purchase #7	$13.98	13.248%	$15.8321	$15.83	$15.85	$15.80
7 purchase totals =	$941.71		$1,030.7164	$1,030.71	$1,030.70	$1,030.70