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	$145.71	10.725%	$161.3374	$161.34	$161.35	$161.30
Purchase #2	$189.83	10.461%	$209.6881	$209.69	$209.70	$209.70
Purchase #3	$243.94	7.637%	$262.5697	$262.57	$262.55	$262.60
Purchase #4	$48.39	5.342%	$50.975	$50.98	$51.00	$51.00
Purchase #5	$214.59	6.175%	$227.8409	$227.84	$227.85	$227.80
Purchase #6	$164.41	4.567%	$171.9186	$171.92	$171.90	$171.90
Purchase #7	$101.50	10.594%	$112.2529	$112.25	$112.25	$112.30
7 purchase totals =	$1,108.37		$1,196.5826	$1,196.59	$1,196.60	$1,196.60