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	$124.83	9.470%	$136.6514	$136.65	$136.65	$136.70
Purchase #2	$184.54	6.591%	$196.703	$196.70	$196.70	$196.70
Purchase #3	$132.69	3.230%	$136.9759	$136.98	$137.00	$137.00
Purchase #4	$108.99	9.110%	$118.919	$118.92	$118.90	$118.90
Purchase #5	$23.97	4.305%	$25.0019	$25.00	$25.00	$25.00
Purchase #6	$39.31	3.702%	$40.7653	$40.77	$40.75	$40.80
Purchase #7	$52.71	12.790%	$59.4516	$59.45	$59.45	$59.50
7 purchase totals =	$667.04		$714.4681	$714.47	$714.45	$714.60