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	$61.80	8.691%	$67.171	$67.17	$67.15	$67.20
Purchase #2	$34.43	10.870%	$38.1725	$38.17	$38.15	$38.20
Purchase #3	$53.91	9.626%	$59.0994	$59.10	$59.10	$59.10
Purchase #4	$182.82	13.863%	$208.1643	$208.16	$208.15	$208.20
Purchase #5	$47.89	13.672%	$54.4375	$54.44	$54.45	$54.40
Purchase #6	$20.40	6.256%	$21.6762	$21.68	$21.70	$21.70
Purchase #7	$228.75	3.296%	$236.2896	$236.29	$236.30	$236.30
7 purchase totals =	$630.00		$685.0105	$685.01	$685.00	$685.10