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	$208.59	12.367%	$234.3863	$234.39	$234.40	$234.40
Purchase #2	$239.73	11.257%	$266.7164	$266.72	$266.70	$266.70
Purchase #3	$88.33	11.305%	$98.3157	$98.32	$98.30	$98.30
Purchase #4	$25.60	12.570%	$28.8179	$28.82	$28.80	$28.80
Purchase #5	$178.39	11.504%	$198.912	$198.91	$198.90	$198.90
Purchase #6	$26.89	3.757%	$27.9003	$27.90	$27.90	$27.90
Purchase #7	$173.80	10.734%	$192.4557	$192.46	$192.45	$192.50
7 purchase totals =	$941.33		$1,047.5043	$1,047.52	$1,047.45	$1,047.50