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	$128.65	8.854%	$140.0407	$140.04	$140.05	$140.00
Purchase #2	$74.46	11.144%	$82.7578	$82.76	$82.75	$82.80
Purchase #3	$63.88	7.215%	$68.4889	$68.49	$68.50	$68.50
Purchase #4	$90.92	11.448%	$101.3285	$101.33	$101.35	$101.30
Purchase #5	$43.72	9.256%	$47.7667	$47.77	$47.75	$47.80
Purchase #6	$7.54	3.763%	$7.8237	$7.82	$7.80	$7.80
Purchase #7	$20.45	4.762%	$21.4238	$21.42	$21.40	$21.40
7 purchase totals =	$429.62		$469.6301	$469.63	$469.60	$469.60