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	$225.62	13.724%	$256.5841	$256.58	$256.60	$256.60
Purchase #2	$224.78	9.201%	$245.462	$245.46	$245.45	$245.50
Purchase #3	$210.80	4.669%	$220.6423	$220.64	$220.65	$220.60
Purchase #4	$174.84	12.138%	$196.0621	$196.06	$196.05	$196.10
Purchase #5	$215.48	11.605%	$240.4865	$240.49	$240.50	$240.50
Purchase #6	$196.38	13.140%	$222.1843	$222.18	$222.20	$222.20
Purchase #7	$74.49	3.308%	$76.9541	$76.95	$76.95	$77.00
7 purchase totals =	$1,322.39		$1,458.3754	$1,458.36	$1,458.40	$1,458.50