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	$132.79	6.725%	$141.7201	$141.72	$141.70	$141.70
Purchase #2	$49.38	6.447%	$52.5635	$52.56	$52.55	$52.60
Purchase #3	$145.67	12.650%	$164.0973	$164.10	$164.10	$164.10
Purchase #4	$230.67	8.361%	$249.9563	$249.96	$249.95	$250.00
Purchase #5	$65.49	10.683%	$72.4863	$72.49	$72.50	$72.50
Purchase #6	$19.89	4.140%	$20.7134	$20.71	$20.70	$20.70
Purchase #7	$198.46	9.645%	$217.6015	$217.60	$217.60	$217.60
7 purchase totals =	$842.35		$919.1384	$919.14	$919.10	$919.20