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	$35.98	13.629%	$40.8837	$40.88	$40.90	$40.90
Purchase #2	$242.59	9.341%	$265.2503	$265.25	$265.25	$265.30
Purchase #3	$242.53	7.802%	$261.4522	$261.45	$261.45	$261.50
Purchase #4	$116.87	4.417%	$122.0321	$122.03	$122.05	$122.00
Purchase #5	$181.75	3.411%	$187.9495	$187.95	$187.95	$187.90
Purchase #6	$54.89	8.568%	$59.593	$59.59	$59.60	$59.60
Purchase #7	$237.51	8.152%	$256.8718	$256.87	$256.85	$256.90
7 purchase totals =	$1,112.12		$1,194.0326	$1,194.02	$1,194.05	$1,194.10