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	$60.29	9.708%	$66.143	$66.14	$66.15	$66.10
Purchase #2	$84.67	6.843%	$90.464	$90.46	$90.45	$90.50
Purchase #3	$201.57	11.569%	$224.8896	$224.89	$224.90	$224.90
Purchase #4	$214.73	5.181%	$225.8552	$225.86	$225.85	$225.90
Purchase #5	$201.30	4.313%	$209.9821	$209.98	$210.00	$210.00
Purchase #6	$38.28	8.701%	$41.6107	$41.61	$41.60	$41.60
Purchase #7	$46.75	10.205%	$51.5208	$51.52	$51.50	$51.50
7 purchase totals =	$847.59		$910.4654	$910.46	$910.45	$910.50