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	$53.53	13.102%	$60.5435	$60.54	$60.55	$60.50
Purchase #2	$190.44	8.681%	$206.9721	$206.97	$206.95	$207.00
Purchase #3	$103.79	7.629%	$111.7081	$111.71	$111.70	$111.70
Purchase #4	$245.97	4.716%	$257.5699	$257.57	$257.55	$257.60
Purchase #5	$136.38	5.472%	$143.8427	$143.84	$143.85	$143.80
Purchase #6	$195.41	13.846%	$222.4665	$222.47	$222.45	$222.50
Purchase #7	$38.80	10.370%	$42.8236	$42.82	$42.80	$42.80
7 purchase totals =	$964.32		$1,045.9264	$1,045.92	$1,045.85	$1,045.90