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	$56.29	12.675%	$63.4248	$63.42	$63.40	$63.40
Purchase #2	$93.26	12.446%	$104.8671	$104.87	$104.85	$104.90
Purchase #3	$59.40	10.638%	$65.719	$65.72	$65.70	$65.70
Purchase #4	$163.82	9.740%	$179.7761	$179.78	$179.80	$179.80
Purchase #5	$151.68	3.387%	$156.8174	$156.82	$156.80	$156.80
Purchase #6	$180.91	8.411%	$196.1263	$196.13	$196.15	$196.10
Purchase #7	$174.68	13.853%	$198.8784	$198.88	$198.90	$198.90
7 purchase totals =	$880.04		$965.6091	$965.62	$965.60	$965.60