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	$136.25	4.641%	$142.5734	$142.57	$142.55	$142.60
Purchase #2	$170.66	4.579%	$178.4745	$178.47	$178.45	$178.50
Purchase #3	$190.82	3.257%	$197.035	$197.04	$197.05	$197.00
Purchase #4	$41.64	12.668%	$46.915	$46.92	$46.90	$46.90
Purchase #5	$95.84	11.771%	$107.1213	$107.12	$107.10	$107.10
Purchase #6	$190.32	13.113%	$215.2767	$215.28	$215.30	$215.30
Purchase #7	$37.79	12.434%	$42.4888	$42.49	$42.50	$42.50
7 purchase totals =	$863.32		$929.8847	$929.89	$929.85	$929.90