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	$132.56	13.678%	$150.6916	$150.69	$150.70	$150.70
Purchase #2	$144.94	13.676%	$164.762	$164.76	$164.75	$164.80
Purchase #3	$168.85	13.649%	$191.8963	$191.90	$191.90	$191.90
Purchase #4	$106.78	6.657%	$113.8883	$113.89	$113.90	$113.90
Purchase #5	$162.47	12.151%	$182.2117	$182.21	$182.20	$182.20
Purchase #6	$51.49	6.296%	$54.7318	$54.73	$54.75	$54.70
Purchase #7	$17.56	6.509%	$18.703	$18.70	$18.70	$18.70
7 purchase totals =	$784.65		$876.8847	$876.88	$876.90	$876.90