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	$222.94	9.645%	$244.4426	$244.44	$244.45	$244.40
Purchase #2	$63.46	6.252%	$67.4275	$67.43	$67.45	$67.40
Purchase #3	$151.46	7.286%	$162.4954	$162.50	$162.50	$162.50
Purchase #4	$57.65	3.368%	$59.5917	$59.59	$59.60	$59.60
Purchase #5	$185.44	10.589%	$205.0762	$205.08	$205.10	$205.10
Purchase #6	$48.49	6.699%	$51.7383	$51.74	$51.75	$51.70
Purchase #7	$140.27	10.854%	$155.4949	$155.49	$155.50	$155.50
7 purchase totals =	$869.71		$946.2666	$946.27	$946.35	$946.20