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	$179.51	9.683%	$196.892	$196.89	$196.90	$196.90
Purchase #2	$94.83	4.507%	$99.104	$99.10	$99.10	$99.10
Purchase #3	$65.66	9.798%	$72.0934	$72.09	$72.10	$72.10
Purchase #4	$146.35	8.471%	$158.7473	$158.75	$158.75	$158.70
Purchase #5	$111.25	6.611%	$118.6047	$118.60	$118.60	$118.60
Purchase #6	$87.67	7.605%	$94.3373	$94.34	$94.35	$94.30
Purchase #7	$22.59	3.505%	$23.3818	$23.38	$23.40	$23.40
7 purchase totals =	$707.86		$763.1605	$763.15	$763.20	$763.10