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	$32.51	5.835%	$34.407	$34.41	$34.40	$34.40
Purchase #2	$6.43	12.614%	$7.2411	$7.24	$7.25	$7.20
Purchase #3	$91.93	8.724%	$99.95	$99.95	$99.95	$100.00
Purchase #4	$12.93	6.757%	$13.8037	$13.80	$13.80	$13.80
Purchase #5	$63.34	7.660%	$68.1918	$68.19	$68.20	$68.20
Purchase #6	$52.57	12.824%	$59.3116	$59.31	$59.30	$59.30
Purchase #7	$97.30	6.467%	$103.5924	$103.59	$103.60	$103.60
7 purchase totals =	$357.01		$386.4976	$386.49	$386.50	$386.50