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	$24.47	4.804%	$25.6455	$25.65	$25.65	$25.60
Purchase #2	$21.76	7.257%	$23.3391	$23.34	$23.35	$23.30
Purchase #3	$51.72	5.179%	$54.3986	$54.40	$54.40	$54.40
Purchase #4	$171.95	3.815%	$178.5099	$178.51	$178.50	$178.50
Purchase #5	$172.50	12.425%	$193.9331	$193.93	$193.95	$193.90
Purchase #6	$59.94	3.218%	$61.8689	$61.87	$61.85	$61.90
Purchase #7	$156.48	7.313%	$167.9234	$167.92	$167.90	$167.90
7 purchase totals =	$658.82		$705.6185	$705.62	$705.60	$705.50