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	$42.62	7.611%	$45.8638	$45.86	$45.85	$45.90
Purchase #2	$117.32	3.478%	$121.4004	$121.40	$121.40	$121.40
Purchase #3	$148.76	10.667%	$164.6282	$164.63	$164.65	$164.60
Purchase #4	$12.28	13.800%	$13.9746	$13.97	$13.95	$14.00
Purchase #5	$217.51	13.508%	$246.8913	$246.89	$246.90	$246.90
Purchase #6	$103.90	9.548%	$113.8204	$113.82	$113.80	$113.80
Purchase #7	$37.89	6.357%	$40.2987	$40.30	$40.30	$40.30
7 purchase totals =	$680.28		$746.8774	$746.87	$746.85	$746.90