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	$97.27	9.574%	$106.5826	$106.58	$106.60	$106.60
Purchase #2	$40.77	7.223%	$43.7148	$43.71	$43.70	$43.70
Purchase #3	$59.42	9.421%	$65.018	$65.02	$65.00	$65.00
Purchase #4	$225.95	3.484%	$233.8221	$233.82	$233.80	$233.80
Purchase #5	$78.92	5.289%	$83.0941	$83.09	$83.10	$83.10
Purchase #6	$213.57	4.239%	$222.6232	$222.62	$222.60	$222.60
Purchase #7	$18.50	11.697%	$20.6639	$20.66	$20.65	$20.70
7 purchase totals =	$734.40		$775.5187	$775.50	$775.45	$775.50