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	$73.70	11.599%	$82.2485	$82.25	$82.25	$82.20
Purchase #2	$186.36	7.131%	$199.6493	$199.65	$199.65	$199.60
Purchase #3	$236.98	7.770%	$255.3933	$255.39	$255.40	$255.40
Purchase #4	$111.32	4.343%	$116.1546	$116.15	$116.15	$116.20
Purchase #5	$14.50	3.527%	$15.0114	$15.01	$15.00	$15.00
Purchase #6	$167.35	12.272%	$187.8872	$187.89	$187.90	$187.90
Purchase #7	$122.79	3.509%	$127.0987	$127.10	$127.10	$127.10
7 purchase totals =	$913.00		$983.4430	$983.44	$983.45	$983.40