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	$40.69	5.789%	$43.0455	$43.05	$43.05	$43.00
Purchase #2	$87.97	5.755%	$93.0327	$93.03	$93.05	$93.00
Purchase #3	$204.67	6.473%	$217.9183	$217.92	$217.90	$217.90
Purchase #4	$117.97	12.274%	$132.4496	$132.45	$132.45	$132.40
Purchase #5	$66.69	10.137%	$73.4504	$73.45	$73.45	$73.50
Purchase #6	$208.39	3.492%	$215.667	$215.67	$215.65	$215.70
Purchase #7	$233.31	4.556%	$243.9396	$243.94	$243.95	$243.90
7 purchase totals =	$959.69		$1,019.5031	$1,019.51	$1,019.50	$1,019.40