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	$60.68	10.664%	$67.1509	$67.15	$67.15	$67.20
Purchase #2	$111.77	5.835%	$118.2918	$118.29	$118.30	$118.30
Purchase #3	$75.92	10.526%	$83.9113	$83.91	$83.90	$83.90
Purchase #4	$97.72	13.729%	$111.136	$111.14	$111.15	$111.10
Purchase #5	$106.85	12.143%	$119.8248	$119.82	$119.80	$119.80
Purchase #6	$73.48	10.413%	$81.1315	$81.13	$81.15	$81.10
Purchase #7	$190.26	7.832%	$205.1612	$205.16	$205.15	$205.20
7 purchase totals =	$716.68		$786.6075	$786.60	$786.60	$786.60