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	$64.70	10.636%	$71.5815	$71.58	$71.60	$71.60
Purchase #2	$56.77	4.237%	$59.1753	$59.18	$59.20	$59.20
Purchase #3	$83.54	6.631%	$89.0795	$89.08	$89.10	$89.10
Purchase #4	$118.67	5.169%	$124.8041	$124.80	$124.80	$124.80
Purchase #5	$225.77	4.441%	$235.7964	$235.80	$235.80	$235.80
Purchase #6	$250.89	8.594%	$272.4515	$272.45	$272.45	$272.50
Purchase #7	$107.33	3.854%	$111.4665	$111.47	$111.45	$111.50
7 purchase totals =	$907.67		$964.3548	$964.36	$964.40	$964.50