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	$100.33	9.213%	$109.5734	$109.57	$109.55	$109.60
Purchase #2	$23.50	8.522%	$25.5027	$25.50	$25.50	$25.50
Purchase #3	$246.54	5.229%	$259.4316	$259.43	$259.45	$259.40
Purchase #4	$105.85	3.509%	$109.5643	$109.56	$109.55	$109.60
Purchase #5	$10.77	6.812%	$11.5037	$11.50	$11.50	$11.50
Purchase #6	$83.26	5.659%	$87.9717	$87.97	$87.95	$88.00
Purchase #7	$207.71	12.578%	$233.8358	$233.84	$233.85	$233.80
7 purchase totals =	$777.96		$837.3832	$837.37	$837.35	$837.40