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	$218.60	9.124%	$238.5451	$238.55	$238.55	$238.50
Purchase #2	$47.27	5.421%	$49.8325	$49.83	$49.85	$49.80
Purchase #3	$41.32	6.218%	$43.8893	$43.89	$43.90	$43.90
Purchase #4	$178.40	6.348%	$189.7248	$189.72	$189.70	$189.70
Purchase #5	$136.80	4.194%	$142.5374	$142.54	$142.55	$142.50
Purchase #6	$60.48	7.353%	$64.9271	$64.93	$64.95	$64.90
Purchase #7	$28.78	12.784%	$32.4592	$32.46	$32.45	$32.50
7 purchase totals =	$711.65		$761.9154	$761.92	$761.95	$761.80