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	$71.71	6.792%	$76.5805	$76.58	$76.60	$76.60
Purchase #2	$197.50	5.668%	$208.6943	$208.69	$208.70	$208.70
Purchase #3	$12.77	4.540%	$13.3498	$13.35	$13.35	$13.30
Purchase #4	$157.64	11.311%	$175.4707	$175.47	$175.45	$175.50
Purchase #5	$234.89	6.690%	$250.6041	$250.60	$250.60	$250.60
Purchase #6	$158.94	3.707%	$164.8319	$164.83	$164.85	$164.80
Purchase #7	$107.69	5.799%	$113.9349	$113.93	$113.95	$113.90
7 purchase totals =	$941.14		$1,003.4662	$1,003.45	$1,003.50	$1,003.40