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	$143.76	10.854%	$159.3637	$159.36	$159.35	$159.40
Purchase #2	$87.34	11.484%	$97.3701	$97.37	$97.35	$97.40
Purchase #3	$168.88	5.724%	$178.5467	$178.55	$178.55	$178.50
Purchase #4	$58.49	5.770%	$61.8649	$61.86	$61.85	$61.90
Purchase #5	$52.25	13.823%	$59.4725	$59.47	$59.45	$59.50
Purchase #6	$159.76	12.216%	$179.2763	$179.28	$179.30	$179.30
Purchase #7	$198.52	10.334%	$219.0351	$219.04	$219.05	$219.00
7 purchase totals =	$869.00		$954.9293	$954.93	$954.90	$955.00