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	$64.69	5.128%	$68.0073	$68.01	$68.00	$68.00
Purchase #2	$92.66	5.351%	$97.6182	$97.62	$97.60	$97.60
Purchase #3	$247.96	11.131%	$275.5604	$275.56	$275.55	$275.60
Purchase #4	$95.32	8.455%	$103.3793	$103.38	$103.40	$103.40
Purchase #5	$44.35	4.791%	$46.4748	$46.47	$46.45	$46.50
Purchase #6	$111.57	5.184%	$117.3538	$117.35	$117.35	$117.40
Purchase #7	$196.38	13.518%	$222.9266	$222.93	$222.95	$222.90
7 purchase totals =	$852.93		$931.3204	$931.32	$931.30	$931.40