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	$207.45	4.522%	$216.8309	$216.83	$216.85	$216.80
Purchase #2	$73.91	13.368%	$83.7903	$83.79	$83.80	$83.80
Purchase #3	$249.68	6.129%	$264.9829	$264.98	$265.00	$265.00
Purchase #4	$188.39	5.383%	$198.531	$198.53	$198.55	$198.50
Purchase #5	$106.83	5.243%	$112.4311	$112.43	$112.45	$112.40
Purchase #6	$39.84	7.633%	$42.881	$42.88	$42.90	$42.90
Purchase #7	$133.54	7.563%	$143.6396	$143.64	$143.65	$143.60
7 purchase totals =	$999.64		$1,063.0868	$1,063.08	$1,063.20	$1,063.00