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	$239.55	6.697%	$255.5927	$255.59	$255.60	$255.60
Purchase #2	$148.41	5.632%	$156.7685	$156.77	$156.75	$156.80
Purchase #3	$227.58	11.343%	$253.3944	$253.39	$253.40	$253.40
Purchase #4	$45.68	4.862%	$47.901	$47.90	$47.90	$47.90
Purchase #5	$76.31	3.138%	$78.7046	$78.70	$78.70	$78.70
Purchase #6	$138.71	4.367%	$144.7675	$144.77	$144.75	$144.80
Purchase #7	$177.84	6.445%	$189.3018	$189.30	$189.30	$189.30
7 purchase totals =	$1,054.08		$1,126.4305	$1,126.42	$1,126.40	$1,126.50