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	$208.47	11.116%	$231.6435	$231.64	$231.65	$231.60
Purchase #2	$171.81	11.565%	$191.6798	$191.68	$191.70	$191.70
Purchase #3	$54.39	9.383%	$59.4934	$59.49	$59.50	$59.50
Purchase #4	$131.97	3.685%	$136.8331	$136.83	$136.85	$136.80
Purchase #5	$166.68	4.565%	$174.2889	$174.29	$174.30	$174.30
Purchase #6	$78.85	12.345%	$88.584	$88.58	$88.60	$88.60
Purchase #7	$146.58	7.769%	$157.9678	$157.97	$157.95	$158.00
7 purchase totals =	$958.75		$1,040.4905	$1,040.48	$1,040.55	$1,040.50