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	$132.93	7.216%	$142.5222	$142.52	$142.50	$142.50
Purchase #2	$71.57	13.775%	$81.4288	$81.43	$81.45	$81.40
Purchase #3	$53.99	7.105%	$57.826	$57.83	$57.85	$57.80
Purchase #4	$27.85	6.302%	$29.6051	$29.61	$29.60	$29.60
Purchase #5	$11.51	3.179%	$11.8759	$11.88	$11.90	$11.90
Purchase #6	$217.25	4.168%	$226.305	$226.31	$226.30	$226.30
Purchase #7	$128.38	10.163%	$141.4273	$141.43	$141.45	$141.40
7 purchase totals =	$643.48		$690.9903	$691.01	$691.05	$690.90