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	$221.34	9.752%	$242.9251	$242.93	$242.95	$242.90
Purchase #2	$70.25	9.284%	$76.772	$76.77	$76.75	$76.80
Purchase #3	$223.85	11.156%	$248.8227	$248.82	$248.80	$248.80
Purchase #4	$113.43	4.393%	$118.413	$118.41	$118.40	$118.40
Purchase #5	$65.89	3.148%	$67.9642	$67.96	$67.95	$68.00
Purchase #6	$73.29	12.687%	$82.5883	$82.59	$82.60	$82.60
Purchase #7	$73.58	10.624%	$81.3971	$81.40	$81.40	$81.40
7 purchase totals =	$841.63		$918.8824	$918.88	$918.85	$918.90