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	$43.70	4.396%	$45.6211	$45.62	$45.60	$45.60
Purchase #2	$210.25	7.264%	$225.5226	$225.52	$225.50	$225.50
Purchase #3	$142.36	13.584%	$161.6982	$161.70	$161.70	$161.70
Purchase #4	$127.26	8.267%	$137.7806	$137.78	$137.80	$137.80
Purchase #5	$125.39	5.377%	$132.1322	$132.13	$132.15	$132.10
Purchase #6	$45.59	3.662%	$47.2595	$47.26	$47.25	$47.30
Purchase #7	$238.40	13.208%	$269.8879	$269.89	$269.90	$269.90
7 purchase totals =	$932.95		$1,019.9021	$1,019.90	$1,019.90	$1,019.90