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	$233.61	9.394%	$255.5553	$255.56	$255.55	$255.60
Purchase #2	$144.41	13.183%	$163.4476	$163.45	$163.45	$163.40
Purchase #3	$145.37	5.256%	$153.0106	$153.01	$153.00	$153.00
Purchase #4	$73.27	5.857%	$77.5614	$77.56	$77.55	$77.60
Purchase #5	$103.85	10.574%	$114.8311	$114.83	$114.85	$114.80
Purchase #6	$223.27	3.803%	$231.761	$231.76	$231.75	$231.80
Purchase #7	$11.73	10.186%	$12.9248	$12.92	$12.90	$12.90
7 purchase totals =	$935.51		$1,009.0918	$1,009.09	$1,009.05	$1,009.10