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	$78.67	8.849%	$85.6315	$85.63	$85.65	$85.60
Purchase #2	$141.46	12.445%	$159.0647	$159.06	$159.05	$159.10
Purchase #3	$181.67	13.298%	$205.8285	$205.83	$205.85	$205.80
Purchase #4	$107.86	10.670%	$119.3687	$119.37	$119.35	$119.40
Purchase #5	$136.81	11.852%	$153.0247	$153.02	$153.00	$153.00
Purchase #6	$68.89	5.146%	$72.4351	$72.44	$72.45	$72.40
Purchase #7	$172.72	3.328%	$178.4681	$178.47	$178.45	$178.50
7 purchase totals =	$888.08		$973.8213	$973.82	$973.80	$973.80