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	$48.27	12.162%	$54.1406	$54.14	$54.15	$54.10
Purchase #2	$100.61	3.265%	$103.8949	$103.89	$103.90	$103.90
Purchase #3	$101.48	6.452%	$108.0275	$108.03	$108.05	$108.00
Purchase #4	$186.64	9.150%	$203.7176	$203.72	$203.70	$203.70
Purchase #5	$236.50	11.418%	$263.5036	$263.50	$263.50	$263.50
Purchase #6	$162.42	11.577%	$181.2234	$181.22	$181.20	$181.20
Purchase #7	$123.93	12.546%	$139.4783	$139.48	$139.50	$139.50
7 purchase totals =	$959.85		$1,053.9859	$1,053.98	$1,054.00	$1,053.90