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	$37.26	3.354%	$38.5097	$38.51	$38.50	$38.50
Purchase #2	$163.34	13.847%	$185.9577	$185.96	$185.95	$186.00
Purchase #3	$73.42	10.181%	$80.8949	$80.89	$80.90	$80.90
Purchase #4	$128.39	11.821%	$143.567	$143.57	$143.55	$143.60
Purchase #5	$112.53	6.381%	$119.7105	$119.71	$119.70	$119.70
Purchase #6	$155.35	8.492%	$168.5423	$168.54	$168.55	$168.50
Purchase #7	$236.69	9.584%	$259.3744	$259.37	$259.35	$259.40
7 purchase totals =	$906.98		$996.5565	$996.55	$996.50	$996.60