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	$166.96	4.483%	$174.4448	$174.44	$174.45	$174.40
Purchase #2	$112.34	6.327%	$119.4478	$119.45	$119.45	$119.40
Purchase #3	$190.37	12.789%	$214.7164	$214.72	$214.70	$214.70
Purchase #4	$31.47	11.835%	$35.1945	$35.19	$35.20	$35.20
Purchase #5	$246.50	3.798%	$255.8621	$255.86	$255.85	$255.90
Purchase #6	$234.73	10.143%	$258.5387	$258.54	$258.55	$258.50
Purchase #7	$51.73	5.409%	$54.5281	$54.53	$54.55	$54.50
7 purchase totals =	$1,034.10		$1,112.7324	$1,112.73	$1,112.75	$1,112.60