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	$66.62	11.144%	$74.0441	$74.04	$74.05	$74.00
Purchase #2	$241.48	10.510%	$266.8595	$266.86	$266.85	$266.90
Purchase #3	$207.48	3.545%	$214.8352	$214.84	$214.85	$214.80
Purchase #4	$24.90	10.667%	$27.5561	$27.56	$27.55	$27.60
Purchase #5	$83.49	3.718%	$86.5942	$86.59	$86.60	$86.60
Purchase #6	$78.99	13.405%	$89.5786	$89.58	$89.60	$89.60
Purchase #7	$142.30	12.443%	$160.0064	$160.01	$160.00	$160.00
7 purchase totals =	$845.26		$919.4741	$919.48	$919.50	$919.50