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	$245.77	4.353%	$256.4684	$256.47	$256.45	$256.50
Purchase #2	$133.71	6.507%	$142.4105	$142.41	$142.40	$142.40
Purchase #3	$82.37	6.338%	$87.5906	$87.59	$87.60	$87.60
Purchase #4	$121.87	4.550%	$127.4151	$127.42	$127.40	$127.40
Purchase #5	$250.62	3.575%	$259.5797	$259.58	$259.60	$259.60
Purchase #6	$6.25	8.337%	$6.7711	$6.77	$6.75	$6.80
Purchase #7	$145.95	4.856%	$153.0373	$153.04	$153.05	$153.00
7 purchase totals =	$986.54		$1,033.2727	$1,033.28	$1,033.25	$1,033.30