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	$211.60	5.157%	$222.5122	$222.51	$222.50	$222.50
Purchase #2	$249.43	12.627%	$280.9255	$280.93	$280.95	$280.90
Purchase #3	$174.64	9.522%	$191.2692	$191.27	$191.25	$191.30
Purchase #4	$70.27	7.342%	$75.4292	$75.43	$75.45	$75.40
Purchase #5	$218.58	10.462%	$241.4478	$241.45	$241.45	$241.40
Purchase #6	$250.97	4.558%	$262.4092	$262.41	$262.40	$262.40
Purchase #7	$61.82	12.581%	$69.5976	$69.60	$69.60	$69.60
7 purchase totals =	$1,237.31		$1,343.5907	$1,343.60	$1,343.60	$1,343.50