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	$210.83	8.660%	$229.0879	$229.09	$229.10	$229.10
Purchase #2	$116.34	13.682%	$132.2576	$132.26	$132.25	$132.30
Purchase #3	$55.80	7.509%	$59.99	$59.99	$60.00	$60.00
Purchase #4	$168.78	13.415%	$191.4218	$191.42	$191.40	$191.40
Purchase #5	$68.77	12.116%	$77.1022	$77.10	$77.10	$77.10
Purchase #6	$105.48	6.666%	$112.5113	$112.51	$112.50	$112.50
Purchase #7	$144.86	5.533%	$152.8751	$152.88	$152.90	$152.90
7 purchase totals =	$870.86		$955.2459	$955.25	$955.25	$955.30