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	$217.95	6.640%	$232.4219	$232.42	$232.40	$232.40
Purchase #2	$26.83	6.394%	$28.5455	$28.55	$28.55	$28.50
Purchase #3	$47.59	11.231%	$52.9348	$52.93	$52.95	$52.90
Purchase #4	$14.93	3.659%	$15.4763	$15.48	$15.50	$15.50
Purchase #5	$221.49	8.726%	$240.8172	$240.82	$240.80	$240.80
Purchase #6	$96.45	4.294%	$100.5916	$100.59	$100.60	$100.60
Purchase #7	$92.54	3.128%	$95.4347	$95.43	$95.45	$95.40
7 purchase totals =	$717.78		$766.2220	$766.22	$766.25	$766.10