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	$66.54	4.480%	$69.521	$69.52	$69.50	$69.50
Purchase #2	$246.43	8.267%	$266.8024	$266.80	$266.80	$266.80
Purchase #3	$46.86	12.245%	$52.598	$52.60	$52.60	$52.60
Purchase #4	$237.48	4.215%	$247.4898	$247.49	$247.50	$247.50
Purchase #5	$198.89	12.199%	$223.1526	$223.15	$223.15	$223.20
Purchase #6	$250.76	12.429%	$281.927	$281.93	$281.95	$281.90
Purchase #7	$225.60	13.770%	$256.6651	$256.67	$256.65	$256.70
7 purchase totals =	$1,272.56		$1,398.1559	$1,398.16	$1,398.15	$1,398.20