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	$230.80	10.855%	$255.8533	$255.85	$255.85	$255.90
Purchase #2	$125.57	9.169%	$137.0835	$137.08	$137.10	$137.10
Purchase #3	$20.51	4.146%	$21.3603	$21.36	$21.35	$21.40
Purchase #4	$170.53	3.304%	$176.1643	$176.16	$176.15	$176.20
Purchase #5	$178.28	12.441%	$200.4598	$200.46	$200.45	$200.50
Purchase #6	$188.46	8.479%	$204.4395	$204.44	$204.45	$204.40
Purchase #7	$160.63	5.176%	$168.9442	$168.94	$168.95	$168.90
7 purchase totals =	$1,074.78		$1,164.3049	$1,164.29	$1,164.30	$1,164.40