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	$193.36	11.393%	$215.3895	$215.39	$215.40	$215.40
Purchase #2	$190.60	7.667%	$205.2133	$205.21	$205.20	$205.20
Purchase #3	$23.71	8.464%	$25.7168	$25.72	$25.70	$25.70
Purchase #4	$36.38	13.342%	$41.2338	$41.23	$41.25	$41.20
Purchase #5	$48.82	10.305%	$53.8509	$53.85	$53.85	$53.90
Purchase #6	$242.76	12.643%	$273.4521	$273.45	$273.45	$273.50
Purchase #7	$141.63	9.388%	$154.9262	$154.93	$154.95	$154.90
7 purchase totals =	$877.26		$969.7826	$969.78	$969.80	$969.80