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	$196.81	13.472%	$223.3242	$223.32	$223.30	$223.30
Purchase #2	$6.92	8.423%	$7.5029	$7.50	$7.50	$7.50
Purchase #3	$181.37	4.572%	$189.6622	$189.66	$189.65	$189.70
Purchase #4	$20.48	9.698%	$22.4662	$22.47	$22.45	$22.50
Purchase #5	$128.32	11.105%	$142.5699	$142.57	$142.55	$142.60
Purchase #6	$191.93	11.602%	$214.1977	$214.20	$214.20	$214.20
Purchase #7	$6.39	10.399%	$7.0545	$7.05	$7.05	$7.10
7 purchase totals =	$732.22		$806.7776	$806.77	$806.70	$806.90