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	$166.49	4.417%	$173.8439	$173.84	$173.85	$173.80
Purchase #2	$235.80	9.222%	$257.5455	$257.55	$257.55	$257.50
Purchase #3	$188.80	4.271%	$196.8636	$196.86	$196.85	$196.90
Purchase #4	$56.54	12.402%	$63.5521	$63.55	$63.55	$63.60
Purchase #5	$213.42	8.430%	$231.4113	$231.41	$231.40	$231.40
Purchase #6	$75.42	13.418%	$85.5399	$85.54	$85.55	$85.50
Purchase #7	$125.25	5.239%	$131.8118	$131.81	$131.80	$131.80
7 purchase totals =	$1,061.72		$1,140.5681	$1,140.56	$1,140.55	$1,140.50