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	$158.72	5.370%	$167.2433	$167.24	$167.25	$167.20
Purchase #2	$214.32	7.105%	$229.5474	$229.55	$229.55	$229.50
Purchase #3	$137.38	4.778%	$143.944	$143.94	$143.95	$143.90
Purchase #4	$60.89	9.438%	$66.6368	$66.64	$66.65	$66.60
Purchase #5	$98.37	3.184%	$101.5021	$101.50	$101.50	$101.50
Purchase #6	$26.52	12.263%	$29.7721	$29.77	$29.75	$29.80
Purchase #7	$121.40	13.271%	$137.511	$137.51	$137.50	$137.50
7 purchase totals =	$817.60		$876.1567	$876.15	$876.15	$876.00