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	$246.66	10.407%	$272.3299	$272.33	$272.35	$272.30
Purchase #2	$224.78	13.476%	$255.0714	$255.07	$255.05	$255.10
Purchase #3	$225.27	3.575%	$233.3234	$233.32	$233.30	$233.30
Purchase #4	$193.91	11.826%	$216.8418	$216.84	$216.85	$216.80
Purchase #5	$225.39	4.389%	$235.2824	$235.28	$235.30	$235.30
Purchase #6	$52.97	12.560%	$59.623	$59.62	$59.60	$59.60
Purchase #7	$219.79	8.544%	$238.5689	$238.57	$238.55	$238.60
7 purchase totals =	$1,388.77		$1,511.0408	$1,511.03	$1,511.00	$1,511.00