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	$93.49	9.484%	$102.3566	$102.36	$102.35	$102.40
Purchase #2	$18.90	8.484%	$20.5035	$20.50	$20.50	$20.50
Purchase #3	$20.25	5.827%	$21.43	$21.43	$21.45	$21.40
Purchase #4	$79.96	9.105%	$87.2404	$87.24	$87.25	$87.20
Purchase #5	$177.35	10.709%	$196.3424	$196.34	$196.35	$196.30
Purchase #6	$111.27	13.809%	$126.6353	$126.64	$126.65	$126.60
Purchase #7	$62.47	11.398%	$69.5903	$69.59	$69.60	$69.60
7 purchase totals =	$563.69		$624.0985	$624.10	$624.15	$624.00