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	$100.65	4.761%	$105.4419	$105.44	$105.45	$105.40
Purchase #2	$86.44	4.169%	$90.0437	$90.04	$90.05	$90.00
Purchase #3	$105.84	10.483%	$116.9352	$116.94	$116.95	$116.90
Purchase #4	$152.50	9.333%	$166.7328	$166.73	$166.75	$166.70
Purchase #5	$249.40	12.626%	$280.8892	$280.89	$280.90	$280.90
Purchase #6	$153.53	7.769%	$165.4577	$165.46	$165.45	$165.50
Purchase #7	$154.58	12.245%	$173.5083	$173.51	$173.50	$173.50
7 purchase totals =	$1,002.94		$1,099.0088	$1,099.01	$1,099.05	$1,098.90