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	$197.60	11.426%	$220.1778	$220.18	$220.20	$220.20
Purchase #2	$55.59	12.584%	$62.5854	$62.59	$62.60	$62.60
Purchase #3	$22.33	7.405%	$23.9835	$23.98	$24.00	$24.00
Purchase #4	$38.43	6.258%	$40.8349	$40.83	$40.85	$40.80
Purchase #5	$36.99	4.338%	$38.5946	$38.59	$38.60	$38.60
Purchase #6	$192.26	4.186%	$200.308	$200.31	$200.30	$200.30
Purchase #7	$137.80	12.184%	$154.5896	$154.59	$154.60	$154.60
7 purchase totals =	$681.00		$741.0738	$741.07	$741.15	$741.10