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	$117.98	4.328%	$123.0862	$123.09	$123.10	$123.10
Purchase #2	$37.68	3.142%	$38.8639	$38.86	$38.85	$38.90
Purchase #3	$143.27	5.712%	$151.4536	$151.45	$151.45	$151.50
Purchase #4	$194.64	8.337%	$210.8671	$210.87	$210.85	$210.90
Purchase #5	$85.45	4.485%	$89.2824	$89.28	$89.30	$89.30
Purchase #6	$204.28	11.253%	$227.2676	$227.27	$227.25	$227.30
Purchase #7	$116.49	11.863%	$130.3092	$130.31	$130.30	$130.30
7 purchase totals =	$899.79		$971.1300	$971.13	$971.10	$971.30