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	$65.70	10.552%	$72.6327	$72.63	$72.65	$72.60
Purchase #2	$44.46	11.617%	$49.6249	$49.62	$49.60	$49.60
Purchase #3	$96.54	8.363%	$104.6136	$104.61	$104.60	$104.60
Purchase #4	$25.58	9.396%	$27.9835	$27.98	$28.00	$28.00
Purchase #5	$118.85	8.354%	$128.7787	$128.78	$128.80	$128.80
Purchase #6	$241.64	8.459%	$262.0803	$262.08	$262.10	$262.10
Purchase #7	$13.73	10.172%	$15.1266	$15.13	$15.15	$15.10
7 purchase totals =	$606.50		$660.8403	$660.83	$660.90	$660.80