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	$127.30	10.542%	$140.72	$140.72	$140.70	$140.70
Purchase #2	$116.98	9.153%	$127.6872	$127.69	$127.70	$127.70
Purchase #3	$213.88	12.868%	$241.4021	$241.40	$241.40	$241.40
Purchase #4	$104.48	8.298%	$113.1498	$113.15	$113.15	$113.10
Purchase #5	$45.70	5.140%	$48.049	$48.05	$48.05	$48.00
Purchase #6	$90.50	12.204%	$101.5446	$101.54	$101.55	$101.50
Purchase #7	$144.30	8.448%	$156.4905	$156.49	$156.50	$156.50
7 purchase totals =	$843.14		$929.0432	$929.04	$929.05	$928.90