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	$172.84	13.418%	$196.0317	$196.03	$196.05	$196.00
Purchase #2	$176.26	8.177%	$190.6728	$190.67	$190.65	$190.70
Purchase #3	$173.91	6.138%	$184.5846	$184.58	$184.60	$184.60
Purchase #4	$213.61	10.401%	$235.8276	$235.83	$235.85	$235.80
Purchase #5	$36.69	9.723%	$40.2574	$40.26	$40.25	$40.30
Purchase #6	$105.53	11.716%	$117.8939	$117.89	$117.90	$117.90
Purchase #7	$18.64	12.787%	$21.0235	$21.02	$21.00	$21.00
7 purchase totals =	$897.48		$986.2915	$986.28	$986.30	$986.30