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	$138.82	9.283%	$151.7067	$151.71	$151.70	$151.70
Purchase #2	$37.63	5.203%	$39.5879	$39.59	$39.60	$39.60
Purchase #3	$76.79	3.442%	$79.4331	$79.43	$79.45	$79.40
Purchase #4	$165.29	3.482%	$171.0454	$171.05	$171.05	$171.00
Purchase #5	$117.84	7.756%	$126.9797	$126.98	$127.00	$127.00
Purchase #6	$36.89	4.287%	$38.4715	$38.47	$38.45	$38.50
Purchase #7	$94.83	9.228%	$103.5809	$103.58	$103.60	$103.60
7 purchase totals =	$668.09		$710.8052	$710.81	$710.85	$710.80