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	$242.79	9.491%	$265.8332	$265.83	$265.85	$265.80
Purchase #2	$47.76	4.567%	$49.9412	$49.94	$49.95	$49.90
Purchase #3	$38.78	12.286%	$43.5445	$43.54	$43.55	$43.50
Purchase #4	$95.82	13.607%	$108.8582	$108.86	$108.85	$108.90
Purchase #5	$78.33	5.249%	$82.4415	$82.44	$82.45	$82.40
Purchase #6	$82.53	4.530%	$86.2686	$86.27	$86.25	$86.30
Purchase #7	$60.86	13.321%	$68.9672	$68.97	$68.95	$69.00
7 purchase totals =	$646.87		$705.8544	$705.85	$705.85	$705.80