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	$24.61	5.385%	$25.9352	$25.94	$25.95	$25.90
Purchase #2	$123.64	7.675%	$133.1294	$133.13	$133.15	$133.10
Purchase #3	$148.43	12.398%	$166.8324	$166.83	$166.85	$166.80
Purchase #4	$61.37	10.553%	$67.8464	$67.85	$67.85	$67.80
Purchase #5	$75.68	8.301%	$81.9622	$81.96	$81.95	$82.00
Purchase #6	$52.95	4.615%	$55.3936	$55.39	$55.40	$55.40
Purchase #7	$142.59	9.585%	$156.2573	$156.26	$156.25	$156.30
7 purchase totals =	$629.27		$687.3565	$687.36	$687.40	$687.30