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	$145.69	3.466%	$150.7396	$150.74	$150.75	$150.70
Purchase #2	$52.51	13.208%	$59.4455	$59.45	$59.45	$59.40
Purchase #3	$246.78	5.128%	$259.4349	$259.43	$259.45	$259.40
Purchase #4	$197.43	6.567%	$210.3952	$210.40	$210.40	$210.40
Purchase #5	$50.34	10.862%	$55.8079	$55.81	$55.80	$55.80
Purchase #6	$33.64	8.492%	$36.4967	$36.50	$36.50	$36.50
Purchase #7	$21.91	5.737%	$23.167	$23.17	$23.15	$23.20
7 purchase totals =	$748.30		$795.4868	$795.50	$795.50	$795.40