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	$133.96	9.611%	$146.8349	$146.83	$146.85	$146.80
Purchase #2	$195.97	9.659%	$214.8987	$214.90	$214.90	$214.90
Purchase #3	$11.32	6.499%	$12.0557	$12.06	$12.05	$12.10
Purchase #4	$90.92	13.565%	$103.2533	$103.25	$103.25	$103.30
Purchase #5	$250.73	8.631%	$272.3705	$272.37	$272.35	$272.40
Purchase #6	$184.76	12.598%	$208.0361	$208.04	$208.05	$208.00
Purchase #7	$162.92	10.104%	$179.3814	$179.38	$179.40	$179.40
7 purchase totals =	$1,030.58		$1,136.8306	$1,136.83	$1,136.85	$1,136.90