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	$210.70	12.871%	$237.8192	$237.82	$237.80	$237.80
Purchase #2	$151.98	10.738%	$168.2996	$168.30	$168.30	$168.30
Purchase #3	$90.67	5.645%	$95.7883	$95.79	$95.80	$95.80
Purchase #4	$55.48	6.646%	$59.1672	$59.17	$59.15	$59.20
Purchase #5	$51.69	9.309%	$56.5018	$56.50	$56.50	$56.50
Purchase #6	$93.48	9.717%	$102.5635	$102.56	$102.55	$102.60
Purchase #7	$132.83	11.807%	$148.5132	$148.51	$148.50	$148.50
7 purchase totals =	$786.83		$868.6528	$868.65	$868.60	$868.70