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	$49.48	10.865%	$54.856	$54.86	$54.85	$54.90
Purchase #2	$21.88	3.321%	$22.6066	$22.61	$22.60	$22.60
Purchase #3	$145.82	8.737%	$158.5603	$158.56	$158.55	$158.60
Purchase #4	$155.44	3.481%	$160.8509	$160.85	$160.85	$160.90
Purchase #5	$139.44	3.578%	$144.4292	$144.43	$144.45	$144.40
Purchase #6	$82.40	12.206%	$92.4577	$92.46	$92.45	$92.50
Purchase #7	$81.87	4.768%	$85.7736	$85.77	$85.75	$85.80
7 purchase totals =	$676.33		$719.5343	$719.54	$719.50	$719.70