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	$140.83	9.734%	$154.5384	$154.54	$154.55	$154.50
Purchase #2	$61.28	7.527%	$65.8925	$65.89	$65.90	$65.90
Purchase #3	$154.33	9.379%	$168.8046	$168.80	$168.80	$168.80
Purchase #4	$230.63	3.291%	$238.22	$238.22	$238.20	$238.20
Purchase #5	$227.27	12.640%	$255.9969	$256.00	$256.00	$256.00
Purchase #6	$94.49	9.802%	$103.7519	$103.75	$103.75	$103.80
Purchase #7	$66.77	10.547%	$73.8122	$73.81	$73.80	$73.80
7 purchase totals =	$975.60		$1,061.0165	$1,061.01	$1,061.00	$1,061.00