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	$38.84	11.852%	$43.4433	$43.44	$43.45	$43.40
Purchase #2	$225.55	3.697%	$233.8886	$233.89	$233.90	$233.90
Purchase #3	$239.72	12.616%	$269.9631	$269.96	$269.95	$270.00
Purchase #4	$42.26	6.863%	$45.1603	$45.16	$45.15	$45.20
Purchase #5	$52.61	12.422%	$59.1452	$59.15	$59.15	$59.10
Purchase #6	$10.79	7.833%	$11.6352	$11.64	$11.65	$11.60
Purchase #7	$157.42	10.680%	$174.2325	$174.23	$174.25	$174.20
7 purchase totals =	$767.19		$837.4682	$837.47	$837.50	$837.40