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	$224.66	12.492%	$252.7245	$252.72	$252.70	$252.70
Purchase #2	$94.70	6.679%	$101.025	$101.03	$101.05	$101.00
Purchase #3	$185.34	13.622%	$210.587	$210.59	$210.60	$210.60
Purchase #4	$133.58	10.116%	$147.093	$147.09	$147.10	$147.10
Purchase #5	$77.52	5.130%	$81.4968	$81.50	$81.50	$81.50
Purchase #6	$77.78	11.782%	$86.944	$86.94	$86.95	$86.90
Purchase #7	$121.72	12.193%	$136.5613	$136.56	$136.55	$136.60
7 purchase totals =	$915.30		$1,016.4316	$1,016.43	$1,016.45	$1,016.40