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	$126.31	11.752%	$141.154	$141.15	$141.15	$141.20
Purchase #2	$126.91	5.142%	$133.4357	$133.44	$133.45	$133.40
Purchase #3	$13.31	9.748%	$14.6075	$14.61	$14.60	$14.60
Purchase #4	$66.47	4.390%	$69.388	$69.39	$69.40	$69.40
Purchase #5	$157.25	9.318%	$171.9026	$171.90	$171.90	$171.90
Purchase #6	$236.44	8.286%	$256.0314	$256.03	$256.05	$256.00
Purchase #7	$186.91	5.186%	$196.6032	$196.60	$196.60	$196.60
7 purchase totals =	$913.60		$983.1224	$983.12	$983.15	$983.10