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	$135.51	11.122%	$150.5814	$150.58	$150.60	$150.60
Purchase #2	$190.78	9.269%	$208.4634	$208.46	$208.45	$208.50
Purchase #3	$51.98	9.273%	$56.8001	$56.80	$56.80	$56.80
Purchase #4	$135.91	6.620%	$144.9072	$144.91	$144.90	$144.90
Purchase #5	$199.37	4.437%	$208.216	$208.22	$208.20	$208.20
Purchase #6	$125.45	13.372%	$142.2252	$142.23	$142.25	$142.20
Purchase #7	$100.25	11.158%	$111.4359	$111.44	$111.45	$111.40
7 purchase totals =	$939.25		$1,022.6292	$1,022.64	$1,022.65	$1,022.60