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	$200.26	8.365%	$217.0117	$217.01	$217.00	$217.00
Purchase #2	$217.56	4.783%	$227.9659	$227.97	$227.95	$228.00
Purchase #3	$246.80	11.768%	$275.8434	$275.84	$275.85	$275.80
Purchase #4	$141.76	10.223%	$156.2521	$156.25	$156.25	$156.30
Purchase #5	$163.52	5.138%	$171.9217	$171.92	$171.90	$171.90
Purchase #6	$77.65	6.124%	$82.4053	$82.41	$82.40	$82.40
Purchase #7	$113.52	12.732%	$127.9734	$127.97	$127.95	$128.00
7 purchase totals =	$1,161.07		$1,259.3735	$1,259.37	$1,259.30	$1,259.40