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	$104.25	8.698%	$113.3177	$113.32	$113.30	$113.30
Purchase #2	$8.94	13.363%	$10.1347	$10.13	$10.15	$10.10
Purchase #3	$31.86	3.243%	$32.8932	$32.89	$32.90	$32.90
Purchase #4	$37.85	3.439%	$39.1517	$39.15	$39.15	$39.20
Purchase #5	$61.92	11.188%	$68.8476	$68.85	$68.85	$68.80
Purchase #6	$171.46	12.333%	$192.6062	$192.61	$192.60	$192.60
Purchase #7	$190.70	10.198%	$210.1476	$210.15	$210.15	$210.10
7 purchase totals =	$606.98		$667.0987	$667.10	$667.10	$667.00