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	$59.36	13.758%	$67.5267	$67.53	$67.55	$67.50
Purchase #2	$70.76	11.357%	$78.7962	$78.80	$78.80	$78.80
Purchase #3	$12.87	7.387%	$13.8207	$13.82	$13.80	$13.80
Purchase #4	$101.96	10.443%	$112.6077	$112.61	$112.60	$112.60
Purchase #5	$97.58	9.756%	$107.0999	$107.10	$107.10	$107.10
Purchase #6	$164.34	13.713%	$186.8759	$186.88	$186.90	$186.90
Purchase #7	$76.56	13.538%	$86.9247	$86.92	$86.90	$86.90
7 purchase totals =	$583.43		$653.6518	$653.66	$653.65	$653.60