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	$82.78	3.389%	$85.5854	$85.59	$85.60	$85.60
Purchase #2	$147.82	4.770%	$154.871	$154.87	$154.85	$154.90
Purchase #3	$196.77	9.386%	$215.2388	$215.24	$215.25	$215.20
Purchase #4	$214.81	7.542%	$231.011	$231.01	$231.00	$231.00
Purchase #5	$145.31	10.298%	$160.274	$160.27	$160.25	$160.30
Purchase #6	$38.81	11.847%	$43.4078	$43.41	$43.40	$43.40
Purchase #7	$121.34	13.424%	$137.6287	$137.63	$137.65	$137.60
7 purchase totals =	$947.64		$1,028.0167	$1,028.02	$1,028.00	$1,028.00