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	$153.46	7.180%	$164.4784	$164.48	$164.50	$164.50
Purchase #2	$82.34	4.540%	$86.0782	$86.08	$86.10	$86.10
Purchase #3	$16.26	10.798%	$18.0158	$18.02	$18.00	$18.00
Purchase #4	$123.89	11.192%	$137.7558	$137.76	$137.75	$137.80
Purchase #5	$10.84	6.497%	$11.5443	$11.54	$11.55	$11.50
Purchase #6	$148.76	5.197%	$156.4911	$156.49	$156.50	$156.50
Purchase #7	$127.78	13.469%	$144.9907	$144.99	$145.00	$145.00
7 purchase totals =	$663.33		$719.3543	$719.36	$719.40	$719.40