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	$109.36	10.594%	$120.9456	$120.95	$120.95	$120.90
Purchase #2	$95.60	10.724%	$105.8521	$105.85	$105.85	$105.90
Purchase #3	$80.52	13.534%	$91.4176	$91.42	$91.40	$91.40
Purchase #4	$144.77	4.622%	$151.4613	$151.46	$151.45	$151.50
Purchase #5	$16.86	3.624%	$17.471	$17.47	$17.45	$17.50
Purchase #6	$237.34	13.580%	$269.5708	$269.57	$269.55	$269.60
Purchase #7	$164.42	12.213%	$184.5006	$184.50	$184.50	$184.50
7 purchase totals =	$848.87		$941.2190	$941.22	$941.15	$941.30