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	$127.74	11.570%	$142.5195	$142.52	$142.50	$142.50
Purchase #2	$112.60	12.328%	$126.4813	$126.48	$126.50	$126.50
Purchase #3	$246.81	9.429%	$270.0817	$270.08	$270.10	$270.10
Purchase #4	$23.45	7.193%	$25.1368	$25.14	$25.15	$25.10
Purchase #5	$215.35	4.662%	$225.3896	$225.39	$225.40	$225.40
Purchase #6	$163.96	13.355%	$185.8569	$185.86	$185.85	$185.90
Purchase #7	$55.80	3.832%	$57.9383	$57.94	$57.95	$57.90
7 purchase totals =	$945.71		$1,033.4041	$1,033.41	$1,033.45	$1,033.40