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	$16.31	3.405%	$16.8654	$16.87	$16.85	$16.90
Purchase #2	$61.32	3.111%	$63.2277	$63.23	$63.25	$63.20
Purchase #3	$227.85	7.541%	$245.0322	$245.03	$245.05	$245.00
Purchase #4	$180.49	5.141%	$189.769	$189.77	$189.75	$189.80
Purchase #5	$81.52	12.648%	$91.8306	$91.83	$91.85	$91.80
Purchase #6	$199.78	11.857%	$223.4679	$223.47	$223.45	$223.50
Purchase #7	$158.70	13.246%	$179.7214	$179.72	$179.70	$179.70
7 purchase totals =	$925.97		$1,009.9142	$1,009.92	$1,009.90	$1,009.90