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	$214.85	5.525%	$226.7205	$226.72	$226.70	$226.70
Purchase #2	$56.37	5.729%	$59.5994	$59.60	$59.60	$59.60
Purchase #3	$52.40	4.337%	$54.6726	$54.67	$54.65	$54.70
Purchase #4	$198.50	11.233%	$220.7975	$220.80	$220.80	$220.80
Purchase #5	$40.58	4.117%	$42.2507	$42.25	$42.25	$42.30
Purchase #6	$138.65	8.278%	$150.1274	$150.13	$150.15	$150.10
Purchase #7	$212.88	11.199%	$236.7204	$236.72	$236.70	$236.70
7 purchase totals =	$914.23		$990.8885	$990.89	$990.85	$990.90