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	$31.75	8.638%	$34.4926	$34.49	$34.50	$34.50
Purchase #2	$91.37	3.594%	$94.6538	$94.65	$94.65	$94.70
Purchase #3	$221.98	7.823%	$239.3455	$239.35	$239.35	$239.30
Purchase #4	$223.88	10.179%	$246.6687	$246.67	$246.65	$246.70
Purchase #5	$155.30	8.108%	$167.8917	$167.89	$167.90	$167.90
Purchase #6	$87.89	3.264%	$90.7587	$90.76	$90.75	$90.80
Purchase #7	$214.98	3.462%	$222.4226	$222.42	$222.40	$222.40
7 purchase totals =	$1,027.15		$1,096.2336	$1,096.23	$1,096.20	$1,096.30