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	$233.33	11.619%	$260.4406	$260.44	$260.45	$260.40
Purchase #2	$35.35	8.833%	$38.4725	$38.47	$38.45	$38.50
Purchase #3	$52.93	8.164%	$57.2512	$57.25	$57.25	$57.30
Purchase #4	$105.92	7.261%	$113.6109	$113.61	$113.60	$113.60
Purchase #5	$54.62	5.466%	$57.6055	$57.61	$57.60	$57.60
Purchase #6	$158.53	3.566%	$164.1832	$164.18	$164.20	$164.20
Purchase #7	$163.60	5.351%	$172.3542	$172.35	$172.35	$172.40
7 purchase totals =	$804.28		$863.9181	$863.91	$863.90	$864.00