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	$40.48	7.410%	$43.4796	$43.48	$43.50	$43.50
Purchase #2	$9.67	5.655%	$10.2168	$10.22	$10.20	$10.20
Purchase #3	$210.88	13.593%	$239.5449	$239.54	$239.55	$239.50
Purchase #4	$18.66	10.570%	$20.6324	$20.63	$20.65	$20.60
Purchase #5	$241.43	8.779%	$262.6251	$262.63	$262.65	$262.60
Purchase #6	$56.55	10.691%	$62.5958	$62.60	$62.60	$62.60
Purchase #7	$148.65	10.614%	$164.4277	$164.43	$164.45	$164.40
7 purchase totals =	$726.32		$803.5223	$803.53	$803.60	$803.40