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	$50.80	4.194%	$52.9306	$52.93	$52.95	$52.90
Purchase #2	$52.52	5.147%	$55.2232	$55.22	$55.20	$55.20
Purchase #3	$87.42	9.167%	$95.4338	$95.43	$95.45	$95.40
Purchase #4	$218.93	10.510%	$241.9395	$241.94	$241.95	$241.90
Purchase #5	$19.81	10.362%	$21.8627	$21.86	$21.85	$21.90
Purchase #6	$217.72	12.449%	$244.824	$244.82	$244.80	$244.80
Purchase #7	$236.38	11.387%	$263.2966	$263.30	$263.30	$263.30
7 purchase totals =	$883.58		$975.5104	$975.50	$975.50	$975.40