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	$101.46	9.548%	$111.1474	$111.15	$111.15	$111.10
Purchase #2	$133.93	12.859%	$151.1521	$151.15	$151.15	$151.20
Purchase #3	$178.74	12.237%	$200.6124	$200.61	$200.60	$200.60
Purchase #4	$149.93	5.693%	$158.4655	$158.47	$158.45	$158.50
Purchase #5	$185.58	6.436%	$197.5239	$197.52	$197.50	$197.50
Purchase #6	$94.39	13.444%	$107.0798	$107.08	$107.10	$107.10
Purchase #7	$39.56	13.701%	$44.9801	$44.98	$45.00	$45.00
7 purchase totals =	$883.59		$970.9612	$970.96	$970.95	$971.00