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	$59.34	11.178%	$65.973	$65.97	$65.95	$66.00
Purchase #2	$61.92	7.228%	$66.3956	$66.40	$66.40	$66.40
Purchase #3	$146.32	3.627%	$151.627	$151.63	$151.65	$151.60
Purchase #4	$154.27	5.564%	$162.8536	$162.85	$162.85	$162.90
Purchase #5	$74.83	13.715%	$85.0929	$85.09	$85.10	$85.10
Purchase #6	$58.81	12.161%	$65.9619	$65.96	$65.95	$66.00
Purchase #7	$198.59	7.506%	$213.4962	$213.50	$213.50	$213.50
7 purchase totals =	$754.08		$811.4002	$811.40	$811.40	$811.50