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	$103.68	12.493%	$116.6327	$116.63	$116.65	$116.60
Purchase #2	$184.57	3.814%	$191.6095	$191.61	$191.60	$191.60
Purchase #3	$76.91	6.518%	$81.923	$81.92	$81.90	$81.90
Purchase #4	$248.71	6.863%	$265.779	$265.78	$265.80	$265.80
Purchase #5	$57.33	7.137%	$61.4216	$61.42	$61.40	$61.40
Purchase #6	$126.42	9.631%	$138.5955	$138.60	$138.60	$138.60
Purchase #7	$92.90	8.166%	$100.4862	$100.49	$100.50	$100.50
7 purchase totals =	$890.52		$956.4475	$956.45	$956.45	$956.40