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	$123.55	8.164%	$133.6366	$133.64	$133.65	$133.60
Purchase #2	$10.39	7.857%	$11.2063	$11.21	$11.20	$11.20
Purchase #3	$28.52	11.609%	$31.8309	$31.83	$31.85	$31.80
Purchase #4	$156.93	3.469%	$162.3739	$162.37	$162.35	$162.40
Purchase #5	$43.75	11.711%	$48.8736	$48.87	$48.85	$48.90
Purchase #6	$103.29	8.523%	$112.0934	$112.09	$112.10	$112.10
Purchase #7	$60.63	11.157%	$67.3945	$67.39	$67.40	$67.40
7 purchase totals =	$527.06		$567.4092	$567.40	$567.40	$567.40