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	$62.37	7.549%	$67.0783	$67.08	$67.10	$67.10
Purchase #2	$168.63	4.649%	$176.4696	$176.47	$176.45	$176.50
Purchase #3	$169.77	12.206%	$190.4921	$190.49	$190.50	$190.50
Purchase #4	$85.50	10.647%	$94.6032	$94.60	$94.60	$94.60
Purchase #5	$20.77	10.235%	$22.8958	$22.90	$22.90	$22.90
Purchase #6	$56.90	7.606%	$61.2278	$61.23	$61.25	$61.20
Purchase #7	$43.86	3.260%	$45.2898	$45.29	$45.30	$45.30
7 purchase totals =	$607.80		$658.0566	$658.06	$658.10	$658.10