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	$21.54	4.132%	$22.43	$22.43	$22.45	$22.40
Purchase #2	$179.83	4.335%	$187.6256	$187.63	$187.65	$187.60
Purchase #3	$17.29	11.874%	$19.343	$19.34	$19.35	$19.30
Purchase #4	$93.64	5.229%	$98.5364	$98.54	$98.55	$98.50
Purchase #5	$182.84	4.132%	$190.3949	$190.39	$190.40	$190.40
Purchase #6	$243.28	9.478%	$266.3381	$266.34	$266.35	$266.30
Purchase #7	$63.94	12.845%	$72.1531	$72.15	$72.15	$72.20
7 purchase totals =	$802.36		$856.8211	$856.82	$856.90	$856.70