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	$50.65	9.727%	$55.5767	$55.58	$55.60	$55.60
Purchase #2	$224.44	4.570%	$234.6969	$234.70	$234.70	$234.70
Purchase #3	$53.42	6.419%	$56.849	$56.85	$56.85	$56.80
Purchase #4	$181.59	8.126%	$196.346	$196.35	$196.35	$196.30
Purchase #5	$30.32	13.388%	$34.3792	$34.38	$34.40	$34.40
Purchase #6	$104.82	4.450%	$109.4845	$109.48	$109.50	$109.50
Purchase #7	$116.64	10.312%	$128.6679	$128.67	$128.65	$128.70
7 purchase totals =	$761.88		$816.0002	$816.01	$816.05	$816.00