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	$239.58	6.776%	$255.8139	$255.81	$255.80	$255.80
Purchase #2	$6.90	10.356%	$7.6146	$7.61	$7.60	$7.60
Purchase #3	$33.44	4.322%	$34.8853	$34.89	$34.90	$34.90
Purchase #4	$176.50	5.512%	$186.2287	$186.23	$186.25	$186.20
Purchase #5	$19.43	3.590%	$20.1275	$20.13	$20.15	$20.10
Purchase #6	$143.74	11.150%	$159.767	$159.77	$159.75	$159.80
Purchase #7	$217.55	11.256%	$242.0374	$242.04	$242.05	$242.00
7 purchase totals =	$837.14		$906.4744	$906.48	$906.50	$906.40