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	$42.94	3.429%	$44.4124	$44.41	$44.40	$44.40
Purchase #2	$116.37	13.169%	$131.6948	$131.69	$131.70	$131.70
Purchase #3	$112.32	10.822%	$124.4753	$124.48	$124.50	$124.50
Purchase #4	$226.81	4.386%	$236.7579	$236.76	$236.75	$236.80
Purchase #5	$172.71	13.732%	$196.4265	$196.43	$196.45	$196.40
Purchase #6	$140.86	6.668%	$150.2525	$150.25	$150.25	$150.30
Purchase #7	$71.67	8.284%	$77.6071	$77.61	$77.60	$77.60
7 purchase totals =	$883.68		$961.6265	$961.63	$961.65	$961.70