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	$8.37	12.831%	$9.444	$9.44	$9.45	$9.40
Purchase #2	$67.47	6.710%	$71.9972	$72.00	$72.00	$72.00
Purchase #3	$75.52	12.768%	$85.1624	$85.16	$85.15	$85.20
Purchase #4	$86.43	4.380%	$90.2156	$90.22	$90.20	$90.20
Purchase #5	$225.79	13.344%	$255.9194	$255.92	$255.90	$255.90
Purchase #6	$117.27	7.613%	$126.1978	$126.20	$126.20	$126.20
Purchase #7	$139.67	12.754%	$157.4835	$157.48	$157.50	$157.50
7 purchase totals =	$720.52		$796.4199	$796.42	$796.40	$796.40