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	$106.88	4.106%	$111.2685	$111.27	$111.25	$111.30
Purchase #2	$9.50	13.630%	$10.7949	$10.79	$10.80	$10.80
Purchase #3	$216.57	6.576%	$230.8116	$230.81	$230.80	$230.80
Purchase #4	$107.94	6.187%	$114.6182	$114.62	$114.60	$114.60
Purchase #5	$74.48	11.389%	$82.9625	$82.96	$82.95	$83.00
Purchase #6	$128.73	12.500%	$144.8213	$144.82	$144.80	$144.80
Purchase #7	$63.27	9.302%	$69.1554	$69.16	$69.15	$69.20
7 purchase totals =	$707.37		$764.4324	$764.43	$764.35	$764.50