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	$213.97	6.508%	$227.8952	$227.90	$227.90	$227.90
Purchase #2	$176.54	13.642%	$200.6236	$200.62	$200.60	$200.60
Purchase #3	$150.69	9.383%	$164.8292	$164.83	$164.85	$164.80
Purchase #4	$52.89	12.544%	$59.5245	$59.52	$59.50	$59.50
Purchase #5	$170.30	9.349%	$186.2213	$186.22	$186.20	$186.20
Purchase #6	$56.97	6.245%	$60.5278	$60.53	$60.55	$60.50
Purchase #7	$180.96	3.557%	$187.3967	$187.40	$187.40	$187.40
7 purchase totals =	$1,002.32		$1,087.0183	$1,087.02	$1,087.00	$1,086.90