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	$72.44	11.291%	$80.6192	$80.62	$80.60	$80.60
Purchase #2	$127.55	3.294%	$131.7515	$131.75	$131.75	$131.80
Purchase #3	$155.95	6.142%	$165.5284	$165.53	$165.55	$165.50
Purchase #4	$11.96	8.214%	$12.9424	$12.94	$12.95	$12.90
Purchase #5	$206.47	5.279%	$217.3696	$217.37	$217.35	$217.40
Purchase #6	$55.46	12.169%	$62.2089	$62.21	$62.20	$62.20
Purchase #7	$167.50	10.437%	$184.982	$184.98	$185.00	$185.00
7 purchase totals =	$797.33		$855.4020	$855.40	$855.40	$855.40