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	$218.82	4.111%	$227.8157	$227.82	$227.80	$227.80
Purchase #2	$29.58	13.237%	$33.4955	$33.50	$33.50	$33.50
Purchase #3	$63.96	10.807%	$70.8722	$70.87	$70.85	$70.90
Purchase #4	$242.91	5.650%	$256.6344	$256.63	$256.65	$256.60
Purchase #5	$44.31	11.791%	$49.5346	$49.53	$49.55	$49.50
Purchase #6	$123.29	11.251%	$137.1614	$137.16	$137.15	$137.20
Purchase #7	$192.94	6.494%	$205.4695	$205.47	$205.45	$205.50
7 purchase totals =	$915.81		$980.9833	$980.98	$980.95	$981.00