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	$74.34	11.466%	$82.8638	$82.86	$82.85	$82.90
Purchase #2	$201.37	12.806%	$227.1574	$227.16	$227.15	$227.20
Purchase #3	$204.78	6.693%	$218.4859	$218.49	$218.50	$218.50
Purchase #4	$156.83	7.103%	$167.9696	$167.97	$167.95	$168.00
Purchase #5	$45.47	12.671%	$51.2315	$51.23	$51.25	$51.20
Purchase #6	$224.46	5.822%	$237.5281	$237.53	$237.55	$237.50
Purchase #7	$175.63	6.284%	$186.6666	$186.67	$186.65	$186.70
7 purchase totals =	$1,082.88		$1,171.9029	$1,171.91	$1,171.90	$1,172.00