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	$108.78	8.419%	$117.9382	$117.94	$117.95	$117.90
Purchase #2	$50.43	13.110%	$57.0414	$57.04	$57.05	$57.00
Purchase #3	$250.97	9.329%	$274.383	$274.38	$274.40	$274.40
Purchase #4	$57.35	11.745%	$64.0858	$64.09	$64.10	$64.10
Purchase #5	$135.25	4.595%	$141.4647	$141.46	$141.45	$141.50
Purchase #6	$100.63	4.232%	$104.8887	$104.89	$104.90	$104.90
Purchase #7	$58.90	6.778%	$62.8922	$62.89	$62.90	$62.90
7 purchase totals =	$762.31		$822.6940	$822.69	$822.75	$822.70