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	$242.41	4.196%	$252.5815	$252.58	$252.60	$252.60
Purchase #2	$125.45	11.225%	$139.5318	$139.53	$139.55	$139.50
Purchase #3	$153.67	12.309%	$172.5852	$172.59	$172.60	$172.60
Purchase #4	$222.29	8.147%	$240.4	$240.40	$240.40	$240.40
Purchase #5	$82.67	11.249%	$91.9695	$91.97	$91.95	$92.00
Purchase #6	$148.29	11.722%	$165.6726	$165.67	$165.65	$165.70
Purchase #7	$92.37	10.861%	$102.4023	$102.40	$102.40	$102.40
7 purchase totals =	$1,067.15		$1,165.1429	$1,165.14	$1,165.15	$1,165.20