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	$105.61	13.170%	$119.5188	$119.52	$119.50	$119.50
Purchase #2	$220.29	12.664%	$248.1875	$248.19	$248.20	$248.20
Purchase #3	$189.81	8.416%	$205.7844	$205.78	$205.80	$205.80
Purchase #4	$117.41	11.641%	$131.0777	$131.08	$131.10	$131.10
Purchase #5	$191.45	9.395%	$209.4367	$209.44	$209.45	$209.40
Purchase #6	$154.85	4.863%	$162.3804	$162.38	$162.40	$162.40
Purchase #7	$119.72	3.456%	$123.8575	$123.86	$123.85	$123.90
7 purchase totals =	$1,099.14		$1,200.2430	$1,200.25	$1,200.30	$1,200.30