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	$246.38	6.599%	$262.6386	$262.64	$262.65	$262.60
Purchase #2	$187.31	5.123%	$196.9059	$196.91	$196.90	$196.90
Purchase #3	$46.49	6.438%	$49.483	$49.48	$49.50	$49.50
Purchase #4	$106.58	10.611%	$117.8892	$117.89	$117.90	$117.90
Purchase #5	$149.52	4.724%	$156.5833	$156.58	$156.60	$156.60
Purchase #6	$208.76	8.624%	$226.7635	$226.76	$226.75	$226.80
Purchase #7	$133.30	11.257%	$148.3056	$148.31	$148.30	$148.30
7 purchase totals =	$1,078.34		$1,158.5691	$1,158.57	$1,158.60	$1,158.60