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	$100.25	11.602%	$111.881	$111.88	$111.90	$111.90
Purchase #2	$197.37	9.335%	$215.7945	$215.79	$215.80	$215.80
Purchase #3	$181.59	7.184%	$194.6354	$194.64	$194.65	$194.60
Purchase #4	$250.26	3.728%	$259.5897	$259.59	$259.60	$259.60
Purchase #5	$133.31	7.662%	$143.5242	$143.52	$143.50	$143.50
Purchase #6	$123.87	6.247%	$131.6082	$131.61	$131.60	$131.60
Purchase #7	$94.96	13.113%	$107.4121	$107.41	$107.40	$107.40
7 purchase totals =	$1,081.61		$1,164.4451	$1,164.44	$1,164.45	$1,164.40