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	$214.66	13.608%	$243.8709	$243.87	$243.85	$243.90
Purchase #2	$30.48	3.642%	$31.5901	$31.59	$31.60	$31.60
Purchase #3	$210.92	11.766%	$235.7368	$235.74	$235.75	$235.70
Purchase #4	$50.90	10.411%	$56.1992	$56.20	$56.20	$56.20
Purchase #5	$43.45	4.491%	$45.4013	$45.40	$45.40	$45.40
Purchase #6	$172.89	12.487%	$194.4788	$194.48	$194.50	$194.50
Purchase #7	$38.54	11.597%	$43.0095	$43.01	$43.00	$43.00
7 purchase totals =	$761.84		$850.2866	$850.29	$850.30	$850.30