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	$91.55	13.510%	$103.9184	$103.92	$103.90	$103.90
Purchase #2	$171.84	6.845%	$183.6024	$183.60	$183.60	$183.60
Purchase #3	$108.78	9.548%	$119.1663	$119.17	$119.15	$119.20
Purchase #4	$117.47	8.571%	$127.5384	$127.54	$127.55	$127.50
Purchase #5	$183.99	6.518%	$195.9825	$195.98	$196.00	$196.00
Purchase #6	$189.68	8.377%	$205.5695	$205.57	$205.55	$205.60
Purchase #7	$72.26	11.434%	$80.5222	$80.52	$80.50	$80.50
7 purchase totals =	$935.57		$1,016.2997	$1,016.30	$1,016.25	$1,016.30