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	$185.59	5.578%	$195.9422	$195.94	$195.95	$195.90
Purchase #2	$222.97	13.867%	$253.8892	$253.89	$253.90	$253.90
Purchase #3	$102.36	7.354%	$109.8876	$109.89	$109.90	$109.90
Purchase #4	$108.72	5.509%	$114.7094	$114.71	$114.70	$114.70
Purchase #5	$130.36	11.141%	$144.8834	$144.88	$144.90	$144.90
Purchase #6	$81.44	10.472%	$89.9684	$89.97	$89.95	$90.00
Purchase #7	$36.25	6.407%	$38.5725	$38.57	$38.55	$38.60
7 purchase totals =	$867.69		$947.8527	$947.85	$947.85	$947.90