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	$31.85	11.356%	$35.4669	$35.47	$35.45	$35.50
Purchase #2	$86.50	5.788%	$91.5066	$91.51	$91.50	$91.50
Purchase #3	$94.64	10.155%	$104.2507	$104.25	$104.25	$104.30
Purchase #4	$16.66	5.511%	$17.5781	$17.58	$17.60	$17.60
Purchase #5	$126.67	13.295%	$143.5108	$143.51	$143.50	$143.50
Purchase #6	$112.57	11.656%	$125.6912	$125.69	$125.70	$125.70
Purchase #7	$204.42	8.754%	$222.3149	$222.31	$222.30	$222.30
7 purchase totals =	$673.31		$740.3192	$740.32	$740.30	$740.40