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	$108.32	11.333%	$120.5959	$120.60	$120.60	$120.60
Purchase #2	$13.70	5.596%	$14.4667	$14.47	$14.45	$14.50
Purchase #3	$14.77	3.746%	$15.3233	$15.32	$15.30	$15.30
Purchase #4	$51.76	6.805%	$55.2823	$55.28	$55.30	$55.30
Purchase #5	$127.54	11.348%	$142.0132	$142.01	$142.00	$142.00
Purchase #6	$95.52	3.687%	$99.0418	$99.04	$99.05	$99.00
Purchase #7	$58.59	8.361%	$63.4887	$63.49	$63.50	$63.50
7 purchase totals =	$470.20		$510.2119	$510.21	$510.20	$510.20