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	$182.54	9.843%	$200.5074	$200.51	$200.50	$200.50
Purchase #2	$214.74	4.630%	$224.6825	$224.68	$224.70	$224.70
Purchase #3	$167.39	13.403%	$189.8253	$189.83	$189.85	$189.80
Purchase #4	$154.55	8.422%	$167.5662	$167.57	$167.55	$167.60
Purchase #5	$192.79	13.175%	$218.1901	$218.19	$218.20	$218.20
Purchase #6	$43.77	4.201%	$45.6088	$45.61	$45.60	$45.60
Purchase #7	$111.52	10.646%	$123.3924	$123.39	$123.40	$123.40
7 purchase totals =	$1,067.30		$1,169.7727	$1,169.78	$1,169.80	$1,169.80