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	$109.84	12.106%	$123.1372	$123.14	$123.15	$123.10
Purchase #2	$61.37	9.343%	$67.1038	$67.10	$67.10	$67.10
Purchase #3	$136.93	8.660%	$148.7881	$148.79	$148.80	$148.80
Purchase #4	$161.54	9.738%	$177.2708	$177.27	$177.25	$177.30
Purchase #5	$133.34	4.123%	$138.8376	$138.84	$138.85	$138.80
Purchase #6	$87.49	3.317%	$90.392	$90.39	$90.40	$90.40
Purchase #7	$241.91	11.800%	$270.4554	$270.46	$270.45	$270.50
7 purchase totals =	$932.42		$1,015.9849	$1,015.99	$1,016.00	$1,016.00