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	$55.72	5.630%	$58.857	$58.86	$58.85	$58.90
Purchase #2	$84.88	6.202%	$90.1443	$90.14	$90.15	$90.10
Purchase #3	$63.44	13.835%	$72.2169	$72.22	$72.20	$72.20
Purchase #4	$52.59	13.684%	$59.7864	$59.79	$59.80	$59.80
Purchase #5	$59.99	5.769%	$63.4508	$63.45	$63.45	$63.50
Purchase #6	$176.97	7.639%	$190.4887	$190.49	$190.50	$190.50
Purchase #7	$116.99	5.273%	$123.1589	$123.16	$123.15	$123.20
7 purchase totals =	$610.58		$658.1030	$658.11	$658.10	$658.20