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	$61.66	10.215%	$67.9586	$67.96	$67.95	$68.00
Purchase #2	$167.27	5.508%	$176.4832	$176.48	$176.50	$176.50
Purchase #3	$60.54	7.836%	$65.2839	$65.28	$65.30	$65.30
Purchase #4	$40.56	6.291%	$43.1116	$43.11	$43.10	$43.10
Purchase #5	$196.40	4.538%	$205.3126	$205.31	$205.30	$205.30
Purchase #6	$94.69	8.818%	$103.0398	$103.04	$103.05	$103.00
Purchase #7	$126.56	10.497%	$139.845	$139.85	$139.85	$139.80
7 purchase totals =	$747.68		$801.0347	$801.03	$801.05	$801.00