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	$228.61	10.874%	$253.4691	$253.47	$253.45	$253.50
Purchase #2	$144.41	4.138%	$150.3857	$150.39	$150.40	$150.40
Purchase #3	$178.96	3.321%	$184.9033	$184.90	$184.90	$184.90
Purchase #4	$107.86	11.132%	$119.867	$119.87	$119.85	$119.90
Purchase #5	$225.94	4.214%	$235.4611	$235.46	$235.45	$235.50
Purchase #6	$208.30	12.768%	$234.8957	$234.90	$234.90	$234.90
Purchase #7	$143.35	6.659%	$152.8957	$152.90	$152.90	$152.90
7 purchase totals =	$1,237.43		$1,331.8776	$1,331.89	$1,331.85	$1,332.00