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	$247.42	13.334%	$280.411	$280.41	$280.40	$280.40
Purchase #2	$184.55	8.813%	$200.8144	$200.81	$200.80	$200.80
Purchase #3	$157.37	13.403%	$178.4623	$178.46	$178.45	$178.50
Purchase #4	$100.73	4.594%	$105.3575	$105.36	$105.35	$105.40
Purchase #5	$128.89	9.737%	$141.44	$141.44	$141.45	$141.40
Purchase #6	$119.94	5.326%	$126.328	$126.33	$126.35	$126.30
Purchase #7	$15.48	3.155%	$15.9684	$15.97	$15.95	$16.00
7 purchase totals =	$954.38		$1,048.7816	$1,048.78	$1,048.75	$1,048.80