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	$88.72	9.354%	$97.0189	$97.02	$97.00	$97.00
Purchase #2	$156.67	6.223%	$166.4196	$166.42	$166.40	$166.40
Purchase #3	$160.92	10.330%	$177.543	$177.54	$177.55	$177.50
Purchase #4	$80.25	4.264%	$83.6719	$83.67	$83.65	$83.70
Purchase #5	$222.75	4.872%	$233.6024	$233.60	$233.60	$233.60
Purchase #6	$90.82	11.139%	$100.9364	$100.94	$100.95	$100.90
Purchase #7	$119.51	3.311%	$123.467	$123.47	$123.45	$123.50
7 purchase totals =	$919.64		$982.6592	$982.66	$982.60	$982.60