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	$231.55	10.322%	$255.4506	$255.45	$255.45	$255.50
Purchase #2	$190.47	3.364%	$196.8774	$196.88	$196.90	$196.90
Purchase #3	$178.56	3.367%	$184.5721	$184.57	$184.55	$184.60
Purchase #4	$51.77	5.680%	$54.7105	$54.71	$54.70	$54.70
Purchase #5	$140.35	5.789%	$148.4749	$148.47	$148.45	$148.50
Purchase #6	$124.65	5.313%	$131.2727	$131.27	$131.25	$131.30
Purchase #7	$235.37	7.723%	$253.5476	$253.55	$253.55	$253.50
7 purchase totals =	$1,152.72		$1,224.9058	$1,224.90	$1,224.85	$1,225.00