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	$54.27	11.499%	$60.5105	$60.51	$60.50	$60.50
Purchase #2	$12.66	13.545%	$14.3748	$14.37	$14.35	$14.40
Purchase #3	$248.87	4.615%	$260.3554	$260.36	$260.35	$260.40
Purchase #4	$206.94	5.626%	$218.5824	$218.58	$218.60	$218.60
Purchase #5	$218.58	3.857%	$227.0106	$227.01	$227.00	$227.00
Purchase #6	$156.40	10.566%	$172.9252	$172.93	$172.95	$172.90
Purchase #7	$79.75	13.556%	$90.5609	$90.56	$90.55	$90.60
7 purchase totals =	$977.47		$1,044.3198	$1,044.32	$1,044.30	$1,044.40