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	$134.89	13.626%	$153.2701	$153.27	$153.25	$153.30
Purchase #2	$174.46	12.334%	$195.9779	$195.98	$196.00	$196.00
Purchase #3	$108.94	10.236%	$120.0911	$120.09	$120.10	$120.10
Purchase #4	$135.89	5.866%	$143.8613	$143.86	$143.85	$143.90
Purchase #5	$193.56	10.157%	$213.2199	$213.22	$213.20	$213.20
Purchase #6	$191.63	10.421%	$211.5998	$211.60	$211.60	$211.60
Purchase #7	$44.88	13.680%	$51.0196	$51.02	$51.00	$51.00
7 purchase totals =	$984.25		$1,089.0397	$1,089.04	$1,089.00	$1,089.10