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	$168.92	3.143%	$174.2292	$174.23	$174.25	$174.20
Purchase #2	$70.32	10.102%	$77.4237	$77.42	$77.40	$77.40
Purchase #3	$43.34	5.640%	$45.7844	$45.78	$45.80	$45.80
Purchase #4	$70.89	10.692%	$78.4696	$78.47	$78.45	$78.50
Purchase #5	$89.84	4.433%	$93.8226	$93.82	$93.80	$93.80
Purchase #6	$187.47	11.183%	$208.4348	$208.43	$208.45	$208.40
Purchase #7	$176.48	8.868%	$192.1302	$192.13	$192.15	$192.10
7 purchase totals =	$807.26		$870.2945	$870.28	$870.30	$870.20