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	$240.40	10.716%	$266.1613	$266.16	$266.15	$266.20
Purchase #2	$13.43	11.303%	$14.948	$14.95	$14.95	$14.90
Purchase #3	$81.71	4.397%	$85.3028	$85.30	$85.30	$85.30
Purchase #4	$37.59	13.307%	$42.5921	$42.59	$42.60	$42.60
Purchase #5	$100.29	8.473%	$108.7876	$108.79	$108.80	$108.80
Purchase #6	$88.32	7.480%	$94.9263	$94.93	$94.95	$94.90
Purchase #7	$183.79	13.601%	$208.7873	$208.79	$208.80	$208.80
7 purchase totals =	$745.53		$821.5054	$821.51	$821.55	$821.50