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	$205.58	12.430%	$231.1336	$231.13	$231.15	$231.10
Purchase #2	$99.60	13.293%	$112.8398	$112.84	$112.85	$112.80
Purchase #3	$141.46	3.569%	$146.5087	$146.51	$146.50	$146.50
Purchase #4	$239.35	5.503%	$252.5214	$252.52	$252.50	$252.50
Purchase #5	$138.65	9.838%	$152.2904	$152.29	$152.30	$152.30
Purchase #6	$215.47	3.235%	$222.4405	$222.44	$222.45	$222.40
Purchase #7	$17.37	5.259%	$18.2835	$18.28	$18.30	$18.30
7 purchase totals =	$1,057.48		$1,136.0179	$1,136.01	$1,136.05	$1,135.90