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	$247.80	5.259%	$260.8318	$260.83	$260.85	$260.80
Purchase #2	$167.58	4.381%	$174.9217	$174.92	$174.90	$174.90
Purchase #3	$73.59	12.120%	$82.5091	$82.51	$82.50	$82.50
Purchase #4	$116.90	13.116%	$132.2326	$132.23	$132.25	$132.20
Purchase #5	$94.56	12.858%	$106.7185	$106.72	$106.70	$106.70
Purchase #6	$152.53	12.268%	$171.2424	$171.24	$171.25	$171.20
Purchase #7	$192.87	11.457%	$214.9671	$214.97	$214.95	$215.00
7 purchase totals =	$1,045.83		$1,143.4232	$1,143.42	$1,143.40	$1,143.30