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	$126.50	12.760%	$142.6414	$142.64	$142.65	$142.60
Purchase #2	$82.76	8.210%	$89.5546	$89.55	$89.55	$89.60
Purchase #3	$35.71	10.469%	$39.4485	$39.45	$39.45	$39.40
Purchase #4	$201.47	11.645%	$224.9312	$224.93	$224.95	$224.90
Purchase #5	$239.78	9.563%	$262.7102	$262.71	$262.70	$262.70
Purchase #6	$20.54	4.611%	$21.4871	$21.49	$21.50	$21.50
Purchase #7	$245.70	13.690%	$279.3363	$279.34	$279.35	$279.30
7 purchase totals =	$952.46		$1,060.1093	$1,060.11	$1,060.15	$1,060.00