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	$209.61	11.812%	$234.3691	$234.37	$234.35	$234.40
Purchase #2	$178.56	9.770%	$196.0053	$196.01	$196.00	$196.00
Purchase #3	$211.54	6.329%	$224.9284	$224.93	$224.95	$224.90
Purchase #4	$152.54	12.634%	$171.8119	$171.81	$171.80	$171.80
Purchase #5	$103.75	4.357%	$108.2704	$108.27	$108.25	$108.30
Purchase #6	$90.66	5.186%	$95.3616	$95.36	$95.35	$95.40
Purchase #7	$63.53	8.726%	$69.0736	$69.07	$69.05	$69.10
7 purchase totals =	$1,010.19		$1,099.8203	$1,099.82	$1,099.75	$1,099.90