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	$56.70	13.821%	$64.5365	$64.54	$64.55	$64.50
Purchase #2	$162.80	3.788%	$168.9669	$168.97	$168.95	$169.00
Purchase #3	$196.41	13.174%	$222.2851	$222.29	$222.30	$222.30
Purchase #4	$42.87	11.213%	$47.677	$47.68	$47.70	$47.70
Purchase #5	$163.48	11.247%	$181.8666	$181.87	$181.85	$181.90
Purchase #6	$79.94	12.610%	$90.0204	$90.02	$90.00	$90.00
Purchase #7	$232.88	9.855%	$255.8303	$255.83	$255.85	$255.80
7 purchase totals =	$935.08		$1,031.1828	$1,031.20	$1,031.20	$1,031.20