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	$212.89	7.204%	$228.2266	$228.23	$228.25	$228.20
Purchase #2	$247.48	13.744%	$281.4937	$281.49	$281.50	$281.50
Purchase #3	$210.34	13.597%	$238.9399	$238.94	$238.95	$238.90
Purchase #4	$100.69	12.143%	$112.9168	$112.92	$112.90	$112.90
Purchase #5	$46.25	12.291%	$51.9346	$51.93	$51.95	$51.90
Purchase #6	$45.98	12.229%	$51.6029	$51.60	$51.60	$51.60
Purchase #7	$38.54	12.706%	$43.4369	$43.44	$43.45	$43.40
7 purchase totals =	$902.17		$1,008.5514	$1,008.55	$1,008.60	$1,008.40