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	$65.86	9.564%	$72.1589	$72.16	$72.15	$72.20
Purchase #2	$119.89	9.416%	$131.1788	$131.18	$131.20	$131.20
Purchase #3	$10.56	7.426%	$11.3442	$11.34	$11.35	$11.30
Purchase #4	$218.42	3.682%	$226.4622	$226.46	$226.45	$226.50
Purchase #5	$118.56	3.264%	$122.4298	$122.43	$122.45	$122.40
Purchase #6	$231.35	5.365%	$243.7619	$243.76	$243.75	$243.80
Purchase #7	$177.81	10.508%	$196.4943	$196.49	$196.50	$196.50
7 purchase totals =	$942.45		$1,003.8301	$1,003.82	$1,003.85	$1,003.90