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	$30.78	9.103%	$33.5819	$33.58	$33.60	$33.60
Purchase #2	$64.88	11.576%	$72.3905	$72.39	$72.40	$72.40
Purchase #3	$61.76	9.150%	$67.411	$67.41	$67.40	$67.40
Purchase #4	$234.93	9.746%	$257.8263	$257.83	$257.85	$257.80
Purchase #5	$34.87	9.135%	$38.0554	$38.06	$38.05	$38.10
Purchase #6	$210.31	6.713%	$224.4281	$224.43	$224.45	$224.40
Purchase #7	$30.81	7.867%	$33.2338	$33.23	$33.25	$33.20
7 purchase totals =	$668.34		$726.9270	$726.93	$727.00	$726.90