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	$47.95	4.330%	$50.0262	$50.03	$50.05	$50.00
Purchase #2	$44.56	8.537%	$48.3641	$48.36	$48.35	$48.40
Purchase #3	$172.43	8.752%	$187.5211	$187.52	$187.50	$187.50
Purchase #4	$245.85	13.788%	$279.7478	$279.75	$279.75	$279.70
Purchase #5	$217.31	4.309%	$226.6739	$226.67	$226.65	$226.70
Purchase #6	$81.59	4.774%	$85.4851	$85.49	$85.50	$85.50
Purchase #7	$187.85	11.323%	$209.1203	$209.12	$209.10	$209.10
7 purchase totals =	$997.54		$1,086.9385	$1,086.94	$1,086.90	$1,086.90