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	$102.83	8.268%	$111.332	$111.33	$111.35	$111.30
Purchase #2	$158.85	6.126%	$168.5812	$168.58	$168.60	$168.60
Purchase #3	$232.63	12.668%	$262.0996	$262.10	$262.10	$262.10
Purchase #4	$94.62	5.158%	$99.5005	$99.50	$99.50	$99.50
Purchase #5	$107.70	8.115%	$116.4399	$116.44	$116.45	$116.40
Purchase #6	$209.52	7.130%	$224.4588	$224.46	$224.45	$224.50
Purchase #7	$15.50	9.827%	$17.0232	$17.02	$17.00	$17.00
7 purchase totals =	$921.65		$999.4352	$999.43	$999.45	$999.40