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	$8.42	6.473%	$8.965	$8.97	$8.95	$9.00
Purchase #2	$66.82	6.281%	$71.017	$71.02	$71.00	$71.00
Purchase #3	$95.60	8.646%	$103.8656	$103.87	$103.85	$103.90
Purchase #4	$184.31	3.534%	$190.8235	$190.82	$190.80	$190.80
Purchase #5	$83.68	7.157%	$89.669	$89.67	$89.65	$89.70
Purchase #6	$235.95	7.568%	$253.8067	$253.81	$253.80	$253.80
Purchase #7	$18.93	6.349%	$20.1319	$20.13	$20.15	$20.10
7 purchase totals =	$693.71		$738.2787	$738.29	$738.20	$738.30