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	$241.59	7.541%	$259.8083	$259.81	$259.80	$259.80
Purchase #2	$109.77	8.642%	$119.2563	$119.26	$119.25	$119.30
Purchase #3	$63.41	13.693%	$72.0927	$72.09	$72.10	$72.10
Purchase #4	$100.26	5.461%	$105.7352	$105.74	$105.75	$105.70
Purchase #5	$240.38	3.127%	$247.8967	$247.90	$247.90	$247.90
Purchase #6	$90.35	11.624%	$100.8523	$100.85	$100.85	$100.90
Purchase #7	$201.52	12.821%	$227.3569	$227.36	$227.35	$227.40
7 purchase totals =	$1,047.28		$1,132.9984	$1,133.01	$1,133.00	$1,133.10