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	$108.78	3.293%	$112.3621	$112.36	$112.35	$112.40
Purchase #2	$85.56	5.105%	$89.9278	$89.93	$89.95	$89.90
Purchase #3	$114.39	5.310%	$120.4641	$120.46	$120.45	$120.50
Purchase #4	$163.94	12.205%	$183.9489	$183.95	$183.95	$183.90
Purchase #5	$227.54	12.819%	$256.7084	$256.71	$256.70	$256.70
Purchase #6	$173.56	13.214%	$196.4942	$196.49	$196.50	$196.50
Purchase #7	$80.97	6.729%	$86.4185	$86.42	$86.40	$86.40
7 purchase totals =	$954.74		$1,046.3240	$1,046.32	$1,046.30	$1,046.30