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	$92.68	11.493%	$103.3317	$103.33	$103.35	$103.30
Purchase #2	$111.68	11.856%	$124.9208	$124.92	$124.90	$124.90
Purchase #3	$67.48	5.103%	$70.9235	$70.92	$70.90	$70.90
Purchase #4	$246.91	13.585%	$280.4527	$280.45	$280.45	$280.50
Purchase #5	$47.53	13.638%	$54.0121	$54.01	$54.00	$54.00
Purchase #6	$178.88	6.260%	$190.0779	$190.08	$190.10	$190.10
Purchase #7	$225.66	3.262%	$233.021	$233.02	$233.00	$233.00
7 purchase totals =	$970.82		$1,056.7397	$1,056.73	$1,056.70	$1,056.70