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	$250.95	5.663%	$265.1613	$265.16	$265.15	$265.20
Purchase #2	$109.94	6.615%	$117.2125	$117.21	$117.20	$117.20
Purchase #3	$250.35	6.509%	$266.6453	$266.65	$266.65	$266.60
Purchase #4	$185.66	3.560%	$192.2695	$192.27	$192.25	$192.30
Purchase #5	$141.48	10.512%	$156.3524	$156.35	$156.35	$156.40
Purchase #6	$45.49	6.719%	$48.5465	$48.55	$48.55	$48.50
Purchase #7	$141.54	6.423%	$150.6311	$150.63	$150.65	$150.60
7 purchase totals =	$1,125.41		$1,196.8186	$1,196.82	$1,196.80	$1,196.80