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	$233.93	9.259%	$255.5896	$255.59	$255.60	$255.60
Purchase #2	$104.88	9.193%	$114.5216	$114.52	$114.50	$114.50
Purchase #3	$136.54	3.660%	$141.5374	$141.54	$141.55	$141.50
Purchase #4	$161.27	7.746%	$173.762	$173.76	$173.75	$173.80
Purchase #5	$166.76	11.228%	$185.4838	$185.48	$185.50	$185.50
Purchase #6	$139.94	13.154%	$158.3477	$158.35	$158.35	$158.30
Purchase #7	$184.88	11.587%	$206.302	$206.30	$206.30	$206.30
7 purchase totals =	$1,128.20		$1,235.5441	$1,235.54	$1,235.55	$1,235.50