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	$208.61	11.868%	$233.3678	$233.37	$233.35	$233.40
Purchase #2	$187.83	9.196%	$205.1028	$205.10	$205.10	$205.10
Purchase #3	$72.77	11.188%	$80.9115	$80.91	$80.90	$80.90
Purchase #4	$95.27	8.376%	$103.2498	$103.25	$103.25	$103.20
Purchase #5	$42.89	3.354%	$44.3285	$44.33	$44.35	$44.30
Purchase #6	$228.71	11.653%	$255.3616	$255.36	$255.35	$255.40
Purchase #7	$188.56	13.758%	$214.5021	$214.50	$214.50	$214.50
7 purchase totals =	$1,024.64		$1,136.8241	$1,136.82	$1,136.80	$1,136.80