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	$27.82	7.233%	$29.8322	$29.83	$29.85	$29.80
Purchase #2	$182.47	8.658%	$198.2683	$198.27	$198.25	$198.30
Purchase #3	$221.79	5.271%	$233.4806	$233.48	$233.50	$233.50
Purchase #4	$125.27	11.206%	$139.3078	$139.31	$139.30	$139.30
Purchase #5	$164.50	11.409%	$183.2678	$183.27	$183.25	$183.30
Purchase #6	$41.54	7.709%	$44.7423	$44.74	$44.75	$44.70
Purchase #7	$222.84	4.825%	$233.592	$233.59	$233.60	$233.60
7 purchase totals =	$986.23		$1,062.4910	$1,062.49	$1,062.50	$1,062.50