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	$40.30	3.393%	$41.6674	$41.67	$41.65	$41.70
Purchase #2	$71.87	6.127%	$76.2735	$76.27	$76.25	$76.30
Purchase #3	$174.26	5.116%	$183.1751	$183.18	$183.20	$183.20
Purchase #4	$101.78	7.564%	$109.4786	$109.48	$109.50	$109.50
Purchase #5	$11.89	5.115%	$12.4982	$12.50	$12.50	$12.50
Purchase #6	$87.31	4.724%	$91.4345	$91.43	$91.45	$91.40
Purchase #7	$230.94	12.478%	$259.7567	$259.76	$259.75	$259.80
7 purchase totals =	$718.35		$774.2840	$774.29	$774.30	$774.40