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	$93.70	11.467%	$104.4446	$104.44	$104.45	$104.40
Purchase #2	$120.41	9.652%	$132.032	$132.03	$132.05	$132.00
Purchase #3	$135.37	7.810%	$145.9424	$145.94	$145.95	$145.90
Purchase #4	$208.27	6.866%	$222.5698	$222.57	$222.55	$222.60
Purchase #5	$98.86	6.759%	$105.5419	$105.54	$105.55	$105.50
Purchase #6	$243.36	4.863%	$255.1946	$255.19	$255.20	$255.20
Purchase #7	$87.66	7.361%	$94.1127	$94.11	$94.10	$94.10
7 purchase totals =	$987.63		$1,059.8380	$1,059.82	$1,059.85	$1,059.70