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	$68.47	6.327%	$72.8021	$72.80	$72.80	$72.80
Purchase #2	$65.46	7.350%	$70.2713	$70.27	$70.25	$70.30
Purchase #3	$136.82	6.636%	$145.8994	$145.90	$145.90	$145.90
Purchase #4	$62.27	8.369%	$67.4814	$67.48	$67.50	$67.50
Purchase #5	$15.39	10.447%	$16.9978	$17.00	$17.00	$17.00
Purchase #6	$184.35	10.460%	$203.633	$203.63	$203.65	$203.60
Purchase #7	$95.43	5.523%	$100.7006	$100.70	$100.70	$100.70
7 purchase totals =	$628.19		$677.7856	$677.78	$677.80	$677.80