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	$99.25	12.434%	$111.5907	$111.59	$111.60	$111.60
Purchase #2	$248.45	3.281%	$256.6016	$256.60	$256.60	$256.60
Purchase #3	$117.71	12.624%	$132.5697	$132.57	$132.55	$132.60
Purchase #4	$92.58	7.337%	$99.3726	$99.37	$99.35	$99.40
Purchase #5	$16.83	7.448%	$18.0835	$18.08	$18.10	$18.10
Purchase #6	$213.98	8.855%	$232.9279	$232.93	$232.95	$232.90
Purchase #7	$139.35	7.868%	$150.3141	$150.31	$150.30	$150.30
7 purchase totals =	$928.15		$1,001.4601	$1,001.45	$1,001.45	$1,001.50