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	$112.96	5.258%	$118.8994	$118.90	$118.90	$118.90
Purchase #2	$79.25	12.705%	$89.3187	$89.32	$89.30	$89.30
Purchase #3	$151.57	9.509%	$165.9828	$165.98	$166.00	$166.00
Purchase #4	$24.35	4.139%	$25.3578	$25.36	$25.35	$25.40
Purchase #5	$163.94	3.302%	$169.3533	$169.35	$169.35	$169.40
Purchase #6	$83.29	13.801%	$94.7849	$94.78	$94.80	$94.80
Purchase #7	$87.53	11.718%	$97.7868	$97.79	$97.80	$97.80
7 purchase totals =	$702.89		$761.4837	$761.48	$761.50	$761.60