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	$174.72	13.549%	$198.3928	$198.39	$198.40	$198.40
Purchase #2	$108.89	4.307%	$113.5799	$113.58	$113.60	$113.60
Purchase #3	$140.92	4.470%	$147.2191	$147.22	$147.20	$147.20
Purchase #4	$164.42	3.438%	$170.0728	$170.07	$170.05	$170.10
Purchase #5	$204.82	8.432%	$222.0904	$222.09	$222.10	$222.10
Purchase #6	$100.33	7.168%	$107.5217	$107.52	$107.50	$107.50
Purchase #7	$113.50	13.215%	$128.499	$128.50	$128.50	$128.50
7 purchase totals =	$1,007.60		$1,087.3757	$1,087.37	$1,087.35	$1,087.40