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	$38.89	12.853%	$43.8885	$43.89	$43.90	$43.90
Purchase #2	$177.77	7.412%	$190.9463	$190.95	$190.95	$190.90
Purchase #3	$146.83	12.636%	$165.3834	$165.38	$165.40	$165.40
Purchase #4	$125.96	11.756%	$140.7679	$140.77	$140.75	$140.80
Purchase #5	$224.44	8.751%	$244.0807	$244.08	$244.10	$244.10
Purchase #6	$233.78	9.527%	$256.0522	$256.05	$256.05	$256.10
Purchase #7	$119.89	4.305%	$125.0513	$125.05	$125.05	$125.10
7 purchase totals =	$1,067.56		$1,166.1703	$1,166.17	$1,166.20	$1,166.30