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	$221.88	7.268%	$238.0062	$238.01	$238.00	$238.00
Purchase #2	$136.47	4.458%	$142.5538	$142.55	$142.55	$142.60
Purchase #3	$96.67	3.846%	$100.3879	$100.39	$100.40	$100.40
Purchase #4	$108.61	13.132%	$122.8727	$122.87	$122.85	$122.90
Purchase #5	$16.58	5.290%	$17.4571	$17.46	$17.45	$17.50
Purchase #6	$230.86	3.436%	$238.7923	$238.79	$238.80	$238.80
Purchase #7	$179.75	7.238%	$192.7603	$192.76	$192.75	$192.80
7 purchase totals =	$990.82		$1,052.8303	$1,052.83	$1,052.80	$1,053.00