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	$32.35	9.642%	$35.4692	$35.47	$35.45	$35.50
Purchase #2	$63.43	5.563%	$66.9586	$66.96	$66.95	$67.00
Purchase #3	$26.74	10.563%	$29.5645	$29.56	$29.55	$29.60
Purchase #4	$39.91	6.789%	$42.6195	$42.62	$42.60	$42.60
Purchase #5	$13.90	5.557%	$14.6724	$14.67	$14.65	$14.70
Purchase #6	$100.89	8.216%	$109.1791	$109.18	$109.20	$109.20
Purchase #7	$34.71	10.728%	$38.4337	$38.43	$38.45	$38.40
7 purchase totals =	$311.93		$336.8970	$336.89	$336.85	$337.00