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	$49.63	5.351%	$52.2857	$52.29	$52.30	$52.30
Purchase #2	$48.58	3.606%	$50.3318	$50.33	$50.35	$50.30
Purchase #3	$113.52	8.677%	$123.3701	$123.37	$123.35	$123.40
Purchase #4	$237.35	11.770%	$265.2861	$265.29	$265.30	$265.30
Purchase #5	$150.90	5.248%	$158.8192	$158.82	$158.80	$158.80
Purchase #6	$197.46	12.441%	$222.026	$222.03	$222.05	$222.00
Purchase #7	$72.90	12.103%	$81.7231	$81.72	$81.70	$81.70
7 purchase totals =	$870.34		$953.8420	$953.85	$953.85	$953.80