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	$243.72	4.595%	$254.9189	$254.92	$254.90	$254.90
Purchase #2	$97.89	7.429%	$105.1622	$105.16	$105.15	$105.20
Purchase #3	$87.60	13.504%	$99.4295	$99.43	$99.45	$99.40
Purchase #4	$95.50	13.446%	$108.3409	$108.34	$108.35	$108.30
Purchase #5	$228.81	12.594%	$257.6263	$257.63	$257.65	$257.60
Purchase #6	$188.57	4.296%	$196.671	$196.67	$196.65	$196.70
Purchase #7	$25.50	8.551%	$27.6805	$27.68	$27.70	$27.70
7 purchase totals =	$967.59		$1,049.8293	$1,049.83	$1,049.85	$1,049.80