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	$59.89	8.651%	$65.0711	$65.07	$65.05	$65.10
Purchase #2	$89.54	6.719%	$95.5562	$95.56	$95.55	$95.60
Purchase #3	$74.50	9.693%	$81.7213	$81.72	$81.70	$81.70
Purchase #4	$233.97	5.435%	$246.6863	$246.69	$246.70	$246.70
Purchase #5	$168.74	7.332%	$181.112	$181.11	$181.10	$181.10
Purchase #6	$131.56	6.513%	$140.1285	$140.13	$140.15	$140.10
Purchase #7	$117.28	5.382%	$123.592	$123.59	$123.60	$123.60
7 purchase totals =	$875.48		$933.8674	$933.87	$933.85	$933.90