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	$218.35	4.217%	$227.5578	$227.56	$227.55	$227.60
Purchase #2	$149.25	11.710%	$166.7272	$166.73	$166.75	$166.70
Purchase #3	$32.38	10.814%	$35.8816	$35.88	$35.90	$35.90
Purchase #4	$199.83	12.853%	$225.5141	$225.51	$225.50	$225.50
Purchase #5	$34.78	4.855%	$36.4686	$36.47	$36.45	$36.50
Purchase #6	$181.95	12.509%	$204.7101	$204.71	$204.70	$204.70
Purchase #7	$163.88	9.854%	$180.0287	$180.03	$180.05	$180.00
7 purchase totals =	$980.42		$1,076.8881	$1,076.89	$1,076.90	$1,076.90