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	$140.72	9.724%	$154.4036	$154.40	$154.40	$154.40
Purchase #2	$196.75	8.249%	$212.9799	$212.98	$213.00	$213.00
Purchase #3	$142.94	13.163%	$161.7552	$161.76	$161.75	$161.80
Purchase #4	$193.29	6.287%	$205.4421	$205.44	$205.45	$205.40
Purchase #5	$18.82	12.265%	$21.1283	$21.13	$21.15	$21.10
Purchase #6	$244.43	12.249%	$274.3702	$274.37	$274.35	$274.40
Purchase #7	$158.43	5.256%	$166.7571	$166.76	$166.75	$166.80
7 purchase totals =	$1,095.38		$1,196.8364	$1,196.84	$1,196.85	$1,196.90