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	$219.58	8.510%	$238.2663	$238.27	$238.25	$238.30
Purchase #2	$195.86	10.245%	$215.9259	$215.93	$215.95	$215.90
Purchase #3	$84.67	7.461%	$90.9872	$90.99	$91.00	$91.00
Purchase #4	$116.32	5.837%	$123.1096	$123.11	$123.10	$123.10
Purchase #5	$113.30	12.232%	$127.1589	$127.16	$127.15	$127.20
Purchase #6	$205.25	12.354%	$230.6066	$230.61	$230.60	$230.60
Purchase #7	$43.45	11.503%	$48.4481	$48.45	$48.45	$48.40
7 purchase totals =	$978.43		$1,074.5026	$1,074.52	$1,074.50	$1,074.50