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	$56.28	9.105%	$61.4043	$61.40	$61.40	$61.40
Purchase #2	$88.97	12.710%	$100.2781	$100.28	$100.30	$100.30
Purchase #3	$176.50	8.791%	$192.0161	$192.02	$192.00	$192.00
Purchase #4	$106.98	8.702%	$116.2894	$116.29	$116.30	$116.30
Purchase #5	$180.39	10.841%	$199.9461	$199.95	$199.95	$199.90
Purchase #6	$249.76	5.663%	$263.9039	$263.90	$263.90	$263.90
Purchase #7	$62.83	12.781%	$70.8603	$70.86	$70.85	$70.90
7 purchase totals =	$921.71		$1,004.6982	$1,004.70	$1,004.70	$1,004.70