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	$78.67	11.410%	$87.6462	$87.65	$87.65	$87.60
Purchase #2	$110.39	11.719%	$123.3266	$123.33	$123.35	$123.30
Purchase #3	$85.41	5.428%	$90.0461	$90.05	$90.05	$90.00
Purchase #4	$147.50	10.571%	$163.0922	$163.09	$163.10	$163.10
Purchase #5	$166.29	5.536%	$175.4958	$175.50	$175.50	$175.50
Purchase #6	$173.85	6.702%	$185.5014	$185.50	$185.50	$185.50
Purchase #7	$34.47	8.672%	$37.4592	$37.46	$37.45	$37.50
7 purchase totals =	$796.58		$862.5675	$862.58	$862.60	$862.50