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	$31.95	12.323%	$35.8872	$35.89	$35.90	$35.90
Purchase #2	$95.35	5.718%	$100.8021	$100.80	$100.80	$100.80
Purchase #3	$131.88	10.239%	$145.3832	$145.38	$145.40	$145.40
Purchase #4	$158.83	7.273%	$170.3817	$170.38	$170.40	$170.40
Purchase #5	$74.64	11.254%	$83.04	$83.04	$83.05	$83.00
Purchase #6	$139.76	8.513%	$151.6578	$151.66	$151.65	$151.70
Purchase #7	$65.43	11.766%	$73.1285	$73.13	$73.15	$73.10
7 purchase totals =	$697.84		$760.2805	$760.28	$760.35	$760.30