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	$227.46	12.135%	$255.0623	$255.06	$255.05	$255.10
Purchase #2	$216.29	6.343%	$230.0093	$230.01	$230.00	$230.00
Purchase #3	$183.65	6.788%	$196.1162	$196.12	$196.10	$196.10
Purchase #4	$47.79	8.514%	$51.8588	$51.86	$51.85	$51.90
Purchase #5	$172.70	13.837%	$196.5965	$196.60	$196.60	$196.60
Purchase #6	$168.44	6.224%	$178.9237	$178.92	$178.90	$178.90
Purchase #7	$204.57	10.330%	$225.7021	$225.70	$225.70	$225.70
7 purchase totals =	$1,220.90		$1,334.2689	$1,334.27	$1,334.20	$1,334.30