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	$244.86	7.347%	$262.8499	$262.85	$262.85	$262.80
Purchase #2	$171.69	10.332%	$189.429	$189.43	$189.45	$189.40
Purchase #3	$39.39	13.468%	$44.695	$44.70	$44.70	$44.70
Purchase #4	$122.50	4.785%	$128.3616	$128.36	$128.35	$128.40
Purchase #5	$164.62	7.456%	$176.8941	$176.89	$176.90	$176.90
Purchase #6	$133.83	9.257%	$146.2186	$146.22	$146.20	$146.20
Purchase #7	$126.96	8.456%	$137.6957	$137.70	$137.70	$137.70
7 purchase totals =	$1,003.85		$1,086.1439	$1,086.15	$1,086.15	$1,086.10