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	$200.80	8.510%	$217.8881	$217.89	$217.90	$217.90
Purchase #2	$68.84	11.612%	$76.8337	$76.83	$76.85	$76.80
Purchase #3	$95.39	10.574%	$105.4765	$105.48	$105.50	$105.50
Purchase #4	$216.60	9.486%	$237.1467	$237.15	$237.15	$237.10
Purchase #5	$43.73	5.493%	$46.1321	$46.13	$46.15	$46.10
Purchase #6	$77.72	10.783%	$86.1005	$86.10	$86.10	$86.10
Purchase #7	$152.77	12.742%	$172.236	$172.24	$172.25	$172.20
7 purchase totals =	$855.85		$941.8136	$941.82	$941.90	$941.70