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	$64.63	12.495%	$72.7055	$72.71	$72.70	$72.70
Purchase #2	$77.52	10.123%	$85.3673	$85.37	$85.35	$85.40
Purchase #3	$86.72	4.198%	$90.3605	$90.36	$90.35	$90.40
Purchase #4	$168.85	8.308%	$182.8781	$182.88	$182.90	$182.90
Purchase #5	$156.49	11.361%	$174.2688	$174.27	$174.25	$174.30
Purchase #6	$112.60	9.847%	$123.6877	$123.69	$123.70	$123.70
Purchase #7	$138.35	6.127%	$146.8267	$146.83	$146.85	$146.80
7 purchase totals =	$805.16		$876.0946	$876.11	$876.10	$876.20