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	$43.82	6.443%	$46.6433	$46.64	$46.65	$46.60
Purchase #2	$135.39	6.703%	$144.4652	$144.47	$144.45	$144.50
Purchase #3	$171.93	3.792%	$178.4496	$178.45	$178.45	$178.40
Purchase #4	$189.48	3.636%	$196.3695	$196.37	$196.35	$196.40
Purchase #5	$132.34	4.401%	$138.1643	$138.16	$138.15	$138.20
Purchase #6	$8.82	7.783%	$9.5065	$9.51	$9.50	$9.50
Purchase #7	$148.82	10.792%	$164.8807	$164.88	$164.90	$164.90
7 purchase totals =	$830.60		$878.4791	$878.48	$878.45	$878.50