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	$40.33	7.678%	$43.4265	$43.43	$43.45	$43.40
Purchase #2	$164.29	4.745%	$172.0856	$172.09	$172.10	$172.10
Purchase #3	$98.81	7.808%	$106.5251	$106.53	$106.55	$106.50
Purchase #4	$41.38	12.529%	$46.5645	$46.56	$46.55	$46.60
Purchase #5	$217.85	10.682%	$241.1207	$241.12	$241.10	$241.10
Purchase #6	$51.58	3.103%	$53.1805	$53.18	$53.20	$53.20
Purchase #7	$87.89	7.335%	$94.3367	$94.34	$94.35	$94.30
7 purchase totals =	$702.13		$757.2396	$757.25	$757.30	$757.20