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	$119.27	7.806%	$128.5802	$128.58	$128.60	$128.60
Purchase #2	$165.91	4.249%	$172.9595	$172.96	$172.95	$173.00
Purchase #3	$88.77	12.793%	$100.1263	$100.13	$100.15	$100.10
Purchase #4	$242.40	4.127%	$252.4038	$252.40	$252.40	$252.40
Purchase #5	$35.73	11.531%	$39.85	$39.85	$39.85	$39.90
Purchase #6	$137.35	12.651%	$154.7261	$154.73	$154.75	$154.70
Purchase #7	$208.61	13.474%	$236.7181	$236.72	$236.70	$236.70
7 purchase totals =	$998.04		$1,085.3640	$1,085.37	$1,085.40	$1,085.40