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	$144.47	7.667%	$155.5465	$155.55	$155.55	$155.50
Purchase #2	$240.41	6.245%	$255.4236	$255.42	$255.40	$255.40
Purchase #3	$178.87	3.492%	$185.1161	$185.12	$185.10	$185.10
Purchase #4	$139.79	9.688%	$153.3329	$153.33	$153.35	$153.30
Purchase #5	$219.27	5.273%	$230.8321	$230.83	$230.85	$230.80
Purchase #6	$53.35	11.523%	$59.4975	$59.50	$59.50	$59.50
Purchase #7	$123.27	13.459%	$139.8609	$139.86	$139.85	$139.90
7 purchase totals =	$1,099.43		$1,179.6096	$1,179.61	$1,179.60	$1,179.50