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	$47.57	13.663%	$54.0695	$54.07	$54.05	$54.10
Purchase #2	$109.33	6.833%	$116.8005	$116.80	$116.80	$116.80
Purchase #3	$229.98	7.744%	$247.7897	$247.79	$247.80	$247.80
Purchase #4	$131.91	3.564%	$136.6113	$136.61	$136.60	$136.60
Purchase #5	$216.96	11.462%	$241.828	$241.83	$241.85	$241.80
Purchase #6	$11.83	11.605%	$13.2029	$13.20	$13.20	$13.20
Purchase #7	$172.84	11.176%	$192.1566	$192.16	$192.15	$192.20
7 purchase totals =	$920.42		$1,002.4585	$1,002.46	$1,002.45	$1,002.50