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	$109.43	6.724%	$116.7881	$116.79	$116.80	$116.80
Purchase #2	$134.65	5.491%	$142.0436	$142.04	$142.05	$142.00
Purchase #3	$157.90	9.214%	$172.4489	$172.45	$172.45	$172.40
Purchase #4	$115.93	13.745%	$131.8646	$131.86	$131.85	$131.90
Purchase #5	$160.89	4.796%	$168.6063	$168.61	$168.60	$168.60
Purchase #6	$74.91	4.475%	$78.2622	$78.26	$78.25	$78.30
Purchase #7	$111.43	8.496%	$120.8971	$120.90	$120.90	$120.90
7 purchase totals =	$865.14		$930.9108	$930.91	$930.90	$930.90