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	$41.74	8.526%	$45.2988	$45.30	$45.30	$45.30
Purchase #2	$60.78	4.524%	$63.5297	$63.53	$63.55	$63.50
Purchase #3	$207.34	12.712%	$233.6971	$233.70	$233.70	$233.70
Purchase #4	$11.86	5.278%	$12.486	$12.49	$12.50	$12.50
Purchase #5	$233.38	9.530%	$255.6211	$255.62	$255.60	$255.60
Purchase #6	$237.96	8.638%	$258.515	$258.52	$258.50	$258.50
Purchase #7	$164.87	13.801%	$187.6237	$187.62	$187.60	$187.60
7 purchase totals =	$957.93		$1,056.7714	$1,056.78	$1,056.75	$1,056.70