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	$68.89	3.844%	$71.5381	$71.54	$71.55	$71.50
Purchase #2	$178.97	4.437%	$186.9109	$186.91	$186.90	$186.90
Purchase #3	$33.49	13.857%	$38.1307	$38.13	$38.15	$38.10
Purchase #4	$64.61	9.719%	$70.8894	$70.89	$70.90	$70.90
Purchase #5	$108.81	5.342%	$114.6226	$114.62	$114.60	$114.60
Purchase #6	$136.67	3.584%	$141.5683	$141.57	$141.55	$141.60
Purchase #7	$95.96	12.577%	$108.0289	$108.03	$108.05	$108.00
7 purchase totals =	$687.40		$731.6889	$731.69	$731.70	$731.60