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	$56.86	10.165%	$62.6398	$62.64	$62.65	$62.60
Purchase #2	$175.60	4.734%	$183.9129	$183.91	$183.90	$183.90
Purchase #3	$190.48	9.346%	$208.2823	$208.28	$208.30	$208.30
Purchase #4	$41.56	5.499%	$43.8454	$43.85	$43.85	$43.80
Purchase #5	$48.76	6.455%	$51.9075	$51.91	$51.90	$51.90
Purchase #6	$213.25	8.442%	$231.2526	$231.25	$231.25	$231.30
Purchase #7	$132.90	3.161%	$137.101	$137.10	$137.10	$137.10
7 purchase totals =	$859.41		$918.9415	$918.94	$918.95	$918.90