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	$205.84	4.702%	$215.5186	$215.52	$215.50	$215.50
Purchase #2	$60.68	11.145%	$67.4428	$67.44	$67.45	$67.40
Purchase #3	$209.52	12.307%	$235.3056	$235.31	$235.30	$235.30
Purchase #4	$144.58	7.671%	$155.6707	$155.67	$155.65	$155.70
Purchase #5	$194.75	10.559%	$215.3137	$215.31	$215.30	$215.30
Purchase #6	$182.39	5.593%	$192.5911	$192.59	$192.60	$192.60
Purchase #7	$71.82	9.216%	$78.4389	$78.44	$78.45	$78.40
7 purchase totals =	$1,069.58		$1,160.2814	$1,160.28	$1,160.25	$1,160.20