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	$220.45	8.387%	$238.9391	$238.94	$238.95	$238.90
Purchase #2	$126.59	13.682%	$143.91	$143.91	$143.90	$143.90
Purchase #3	$52.89	13.117%	$59.8276	$59.83	$59.85	$59.80
Purchase #4	$60.75	7.639%	$65.3907	$65.39	$65.40	$65.40
Purchase #5	$98.70	13.443%	$111.9682	$111.97	$111.95	$112.00
Purchase #6	$215.43	12.487%	$242.3307	$242.33	$242.35	$242.30
Purchase #7	$77.98	8.413%	$84.5405	$84.54	$84.55	$84.50
7 purchase totals =	$852.79		$946.9068	$946.91	$946.95	$946.80