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	$134.55	7.438%	$144.5578	$144.56	$144.55	$144.60
Purchase #2	$238.33	11.236%	$265.1088	$265.11	$265.10	$265.10
Purchase #3	$128.71	11.516%	$143.5322	$143.53	$143.55	$143.50
Purchase #4	$245.54	5.824%	$259.8402	$259.84	$259.85	$259.80
Purchase #5	$151.81	10.604%	$167.9079	$167.91	$167.90	$167.90
Purchase #6	$133.65	4.191%	$139.2513	$139.25	$139.25	$139.30
Purchase #7	$214.91	12.466%	$241.7007	$241.70	$241.70	$241.70
7 purchase totals =	$1,247.50		$1,361.8989	$1,361.90	$1,361.90	$1,361.90