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	$182.90	7.222%	$196.109	$196.11	$196.10	$196.10
Purchase #2	$88.41	10.660%	$97.8345	$97.83	$97.85	$97.80
Purchase #3	$195.35	5.239%	$205.5844	$205.58	$205.60	$205.60
Purchase #4	$112.30	9.571%	$123.0482	$123.05	$123.05	$123.00
Purchase #5	$31.87	7.529%	$34.2695	$34.27	$34.25	$34.30
Purchase #6	$141.94	6.254%	$150.8169	$150.82	$150.80	$150.80
Purchase #7	$244.90	8.508%	$265.7361	$265.74	$265.75	$265.70
7 purchase totals =	$997.67		$1,073.3986	$1,073.40	$1,073.40	$1,073.30