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	$10.73	7.624%	$11.5481	$11.55	$11.55	$11.50
Purchase #2	$107.70	3.856%	$111.8529	$111.85	$111.85	$111.90
Purchase #3	$192.38	13.317%	$217.9992	$218.00	$218.00	$218.00
Purchase #4	$158.85	9.256%	$173.5532	$173.55	$173.55	$173.60
Purchase #5	$187.75	10.190%	$206.8817	$206.88	$206.90	$206.90
Purchase #6	$237.68	7.289%	$255.0045	$255.00	$255.00	$255.00
Purchase #7	$112.41	6.769%	$120.019	$120.02	$120.00	$120.00
7 purchase totals =	$1,007.50		$1,096.8586	$1,096.85	$1,096.85	$1,096.90