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	$68.32	11.863%	$76.4248	$76.42	$76.40	$76.40
Purchase #2	$164.61	6.411%	$175.1631	$175.16	$175.15	$175.20
Purchase #3	$187.80	4.759%	$196.7374	$196.74	$196.75	$196.70
Purchase #4	$44.84	4.700%	$46.9475	$46.95	$46.95	$46.90
Purchase #5	$153.96	9.265%	$168.2244	$168.22	$168.20	$168.20
Purchase #6	$84.46	12.357%	$94.8967	$94.90	$94.90	$94.90
Purchase #7	$34.82	10.719%	$38.5524	$38.55	$38.55	$38.60
7 purchase totals =	$738.81		$796.9463	$796.94	$796.90	$796.90