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	$161.43	6.208%	$171.4516	$171.45	$171.45	$171.50
Purchase #2	$212.61	9.804%	$233.4543	$233.45	$233.45	$233.50
Purchase #3	$13.31	8.612%	$14.4563	$14.46	$14.45	$14.50
Purchase #4	$171.71	6.487%	$182.8488	$182.85	$182.85	$182.80
Purchase #5	$145.51	9.787%	$159.7511	$159.75	$159.75	$159.80
Purchase #6	$112.83	13.570%	$128.141	$128.14	$128.15	$128.10
Purchase #7	$46.32	13.806%	$52.7149	$52.71	$52.70	$52.70
7 purchase totals =	$863.72		$942.8180	$942.81	$942.80	$942.90