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	$65.81	8.314%	$71.2814	$71.28	$71.30	$71.30
Purchase #2	$24.32	9.384%	$26.6022	$26.60	$26.60	$26.60
Purchase #3	$89.79	11.329%	$99.9623	$99.96	$99.95	$100.00
Purchase #4	$126.68	4.398%	$132.2514	$132.25	$132.25	$132.30
Purchase #5	$66.83	8.585%	$72.5674	$72.57	$72.55	$72.60
Purchase #6	$111.38	6.281%	$118.3758	$118.38	$118.40	$118.40
Purchase #7	$228.59	5.577%	$241.3385	$241.34	$241.35	$241.30
7 purchase totals =	$713.40		$762.3790	$762.38	$762.40	$762.50