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	$250.43	12.675%	$282.172	$282.17	$282.15	$282.20
Purchase #2	$126.52	4.542%	$132.2665	$132.27	$132.25	$132.30
Purchase #3	$95.30	12.826%	$107.5232	$107.52	$107.50	$107.50
Purchase #4	$155.65	3.490%	$161.0822	$161.08	$161.10	$161.10
Purchase #5	$93.31	7.729%	$100.5219	$100.52	$100.50	$100.50
Purchase #6	$172.91	4.524%	$180.7324	$180.73	$180.75	$180.70
Purchase #7	$70.26	13.312%	$79.613	$79.61	$79.60	$79.60
7 purchase totals =	$964.38		$1,043.9112	$1,043.90	$1,043.85	$1,043.90