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	$47.75	10.565%	$52.7948	$52.79	$52.80	$52.80
Purchase #2	$97.51	7.118%	$104.4508	$104.45	$104.45	$104.50
Purchase #3	$245.54	3.855%	$255.0056	$255.01	$255.00	$255.00
Purchase #4	$103.73	8.421%	$112.4651	$112.47	$112.45	$112.50
Purchase #5	$200.60	4.210%	$209.0453	$209.05	$209.05	$209.00
Purchase #6	$119.86	9.849%	$131.665	$131.67	$131.65	$131.70
Purchase #7	$176.77	9.676%	$193.8743	$193.87	$193.85	$193.90
7 purchase totals =	$991.76		$1,059.3009	$1,059.31	$1,059.25	$1,059.40