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	$142.56	6.199%	$151.3973	$151.40	$151.40	$151.40
Purchase #2	$188.59	10.103%	$207.6432	$207.64	$207.65	$207.60
Purchase #3	$78.71	8.647%	$85.5161	$85.52	$85.50	$85.50
Purchase #4	$106.25	11.295%	$118.2509	$118.25	$118.25	$118.30
Purchase #5	$140.66	5.383%	$148.2317	$148.23	$148.25	$148.20
Purchase #6	$115.89	8.613%	$125.8716	$125.87	$125.85	$125.90
Purchase #7	$130.25	9.323%	$142.3932	$142.39	$142.40	$142.40
7 purchase totals =	$902.91		$979.3040	$979.30	$979.30	$979.30