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	$104.74	10.872%	$116.1273	$116.13	$116.15	$116.10
Purchase #2	$126.46	4.742%	$132.4567	$132.46	$132.45	$132.50
Purchase #3	$63.86	3.191%	$65.8978	$65.90	$65.90	$65.90
Purchase #4	$72.45	6.673%	$77.2846	$77.28	$77.30	$77.30
Purchase #5	$183.51	4.673%	$192.0854	$192.09	$192.10	$192.10
Purchase #6	$166.52	7.773%	$179.4636	$179.46	$179.45	$179.50
Purchase #7	$92.37	12.682%	$104.0844	$104.08	$104.10	$104.10
7 purchase totals =	$809.91		$867.3998	$867.40	$867.45	$867.50