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	$82.68	11.873%	$92.4966	$92.50	$92.50	$92.50
Purchase #2	$82.45	12.835%	$93.0325	$93.03	$93.05	$93.00
Purchase #3	$88.82	13.146%	$100.4963	$100.50	$100.50	$100.50
Purchase #4	$168.32	6.268%	$178.8703	$178.87	$178.85	$178.90
Purchase #5	$150.96	3.403%	$156.0972	$156.10	$156.10	$156.10
Purchase #6	$59.47	9.372%	$65.0435	$65.04	$65.05	$65.00
Purchase #7	$214.68	8.705%	$233.3679	$233.37	$233.35	$233.40
7 purchase totals =	$847.38		$919.4043	$919.41	$919.40	$919.40