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	$31.59	8.472%	$34.2663	$34.27	$34.25	$34.30
Purchase #2	$92.98	8.108%	$100.5188	$100.52	$100.50	$100.50
Purchase #3	$102.43	4.836%	$107.3835	$107.38	$107.40	$107.40
Purchase #4	$133.89	9.191%	$146.1958	$146.20	$146.20	$146.20
Purchase #5	$159.68	4.365%	$166.65	$166.65	$166.65	$166.70
Purchase #6	$136.78	13.497%	$155.2412	$155.24	$155.25	$155.20
Purchase #7	$40.76	11.275%	$45.3557	$45.36	$45.35	$45.40
7 purchase totals =	$698.11		$755.6113	$755.62	$755.60	$755.70