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	$68.72	3.179%	$70.9046	$70.90	$70.90	$70.90
Purchase #2	$30.88	10.102%	$33.9995	$34.00	$34.00	$34.00
Purchase #3	$136.78	4.546%	$142.998	$143.00	$143.00	$143.00
Purchase #4	$56.67	8.633%	$61.5623	$61.56	$61.55	$61.60
Purchase #5	$146.33	6.257%	$155.4859	$155.49	$155.50	$155.50
Purchase #6	$170.83	12.628%	$192.4024	$192.40	$192.40	$192.40
Purchase #7	$69.69	12.455%	$78.3699	$78.37	$78.35	$78.40
7 purchase totals =	$679.90		$735.7226	$735.72	$735.70	$735.80