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	$152.71	10.276%	$168.4025	$168.40	$168.40	$168.40
Purchase #2	$97.42	5.293%	$102.5764	$102.58	$102.60	$102.60
Purchase #3	$245.32	4.261%	$255.7731	$255.77	$255.75	$255.80
Purchase #4	$38.54	7.776%	$41.5369	$41.54	$41.55	$41.50
Purchase #5	$53.85	7.344%	$57.8047	$57.80	$57.80	$57.80
Purchase #6	$76.92	4.461%	$80.3514	$80.35	$80.35	$80.40
Purchase #7	$137.83	3.612%	$142.8084	$142.81	$142.80	$142.80
7 purchase totals =	$802.59		$849.2534	$849.25	$849.25	$849.30