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	$183.47	7.192%	$196.6652	$196.67	$196.65	$196.70
Purchase #2	$164.48	4.832%	$172.4277	$172.43	$172.45	$172.40
Purchase #3	$45.54	13.208%	$51.5549	$51.55	$51.55	$51.60
Purchase #4	$111.75	4.210%	$116.4547	$116.45	$116.45	$116.50
Purchase #5	$116.91	6.416%	$124.4109	$124.41	$124.40	$124.40
Purchase #6	$14.70	4.438%	$15.3524	$15.35	$15.35	$15.40
Purchase #7	$7.32	4.170%	$7.6252	$7.63	$7.65	$7.60
7 purchase totals =	$644.17		$684.4910	$684.49	$684.50	$684.60