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	$141.59	10.849%	$156.9511	$156.95	$156.95	$157.00
Purchase #2	$175.90	11.751%	$196.57	$196.57	$196.55	$196.60
Purchase #3	$207.47	9.447%	$227.0697	$227.07	$227.05	$227.10
Purchase #4	$117.69	4.149%	$122.573	$122.57	$122.55	$122.60
Purchase #5	$140.83	3.590%	$145.8858	$145.89	$145.90	$145.90
Purchase #6	$196.43	13.230%	$222.4177	$222.42	$222.40	$222.40
Purchase #7	$98.70	12.121%	$110.6634	$110.66	$110.65	$110.70
7 purchase totals =	$1,078.61		$1,182.1307	$1,182.13	$1,182.05	$1,182.30