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	$247.55	5.198%	$260.4176	$260.42	$260.40	$260.40
Purchase #2	$106.86	5.368%	$112.5962	$112.60	$112.60	$112.60
Purchase #3	$125.42	6.684%	$133.8031	$133.80	$133.80	$133.80
Purchase #4	$67.87	7.514%	$72.9698	$72.97	$72.95	$73.00
Purchase #5	$124.84	11.411%	$139.0855	$139.09	$139.10	$139.10
Purchase #6	$85.79	4.352%	$89.5236	$89.52	$89.50	$89.50
Purchase #7	$6.72	11.228%	$7.4745	$7.47	$7.45	$7.50
7 purchase totals =	$765.05		$815.8703	$815.87	$815.80	$815.90