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	$157.61	5.372%	$166.0768	$166.08	$166.10	$166.10
Purchase #2	$221.86	13.395%	$251.5781	$251.58	$251.60	$251.60
Purchase #3	$64.98	12.357%	$73.0096	$73.01	$73.00	$73.00
Purchase #4	$222.63	5.320%	$234.4739	$234.47	$234.45	$234.50
Purchase #5	$215.90	10.431%	$238.4205	$238.42	$238.40	$238.40
Purchase #6	$25.47	7.812%	$27.4597	$27.46	$27.45	$27.50
Purchase #7	$123.31	13.204%	$139.5919	$139.59	$139.60	$139.60
7 purchase totals =	$1,031.76		$1,130.6105	$1,130.61	$1,130.60	$1,130.70