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	$134.27	3.834%	$139.4179	$139.42	$139.40	$139.40
Purchase #2	$34.59	6.423%	$36.8117	$36.81	$36.80	$36.80
Purchase #3	$29.58	11.270%	$32.9137	$32.91	$32.90	$32.90
Purchase #4	$45.49	6.831%	$48.5974	$48.60	$48.60	$48.60
Purchase #5	$61.93	5.437%	$65.2971	$65.30	$65.30	$65.30
Purchase #6	$153.91	6.606%	$164.0773	$164.08	$164.10	$164.10
Purchase #7	$207.80	13.773%	$236.4203	$236.42	$236.40	$236.40
7 purchase totals =	$667.57		$723.5354	$723.54	$723.50	$723.50