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	$101.78	8.616%	$110.5494	$110.55	$110.55	$110.50
Purchase #2	$214.41	8.715%	$233.0958	$233.10	$233.10	$233.10
Purchase #3	$245.45	6.732%	$261.9737	$261.97	$261.95	$262.00
Purchase #4	$134.36	5.406%	$141.6235	$141.62	$141.60	$141.60
Purchase #5	$69.86	10.859%	$77.4461	$77.45	$77.45	$77.40
Purchase #6	$89.57	12.153%	$100.4554	$100.46	$100.45	$100.50
Purchase #7	$63.99	12.869%	$72.2249	$72.22	$72.20	$72.20
7 purchase totals =	$919.42		$997.3688	$997.37	$997.30	$997.30