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	$32.69	6.839%	$34.9257	$34.93	$34.95	$34.90
Purchase #2	$126.48	4.456%	$132.1159	$132.12	$132.10	$132.10
Purchase #3	$94.46	10.648%	$104.5181	$104.52	$104.50	$104.50
Purchase #4	$71.90	4.280%	$74.9773	$74.98	$75.00	$75.00
Purchase #5	$82.89	6.863%	$88.5787	$88.58	$88.60	$88.60
Purchase #6	$51.81	6.671%	$55.2662	$55.27	$55.25	$55.30
Purchase #7	$227.59	13.256%	$257.7593	$257.76	$257.75	$257.80
7 purchase totals =	$687.82		$748.1412	$748.16	$748.15	$748.20