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	$112.95	9.301%	$123.4555	$123.46	$123.45	$123.50
Purchase #2	$134.69	10.440%	$148.7516	$148.75	$148.75	$148.80
Purchase #3	$210.94	8.176%	$228.1865	$228.19	$228.20	$228.20
Purchase #4	$244.55	4.863%	$256.4425	$256.44	$256.45	$256.40
Purchase #5	$35.50	8.405%	$38.4838	$38.48	$38.50	$38.50
Purchase #6	$166.96	10.671%	$184.7763	$184.78	$184.80	$184.80
Purchase #7	$23.57	9.547%	$25.8202	$25.82	$25.80	$25.80
7 purchase totals =	$929.16		$1,005.9164	$1,005.92	$1,005.95	$1,006.00