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	$156.36	12.198%	$175.4328	$175.43	$175.45	$175.40
Purchase #2	$216.94	13.824%	$246.9298	$246.93	$246.95	$246.90
Purchase #3	$98.67	13.261%	$111.7546	$111.75	$111.75	$111.80
Purchase #4	$137.68	9.333%	$150.5297	$150.53	$150.55	$150.50
Purchase #5	$72.60	6.690%	$77.4569	$77.46	$77.45	$77.50
Purchase #6	$200.93	11.867%	$224.7744	$224.77	$224.75	$224.80
Purchase #7	$69.60	4.762%	$72.9144	$72.91	$72.90	$72.90
7 purchase totals =	$952.78		$1,059.7926	$1,059.78	$1,059.80	$1,059.80