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	$57.54	8.722%	$62.5586	$62.56	$62.55	$62.60
Purchase #2	$70.37	12.854%	$79.4154	$79.42	$79.40	$79.40
Purchase #3	$182.32	7.665%	$196.2948	$196.29	$196.30	$196.30
Purchase #4	$19.38	3.397%	$20.0383	$20.04	$20.05	$20.00
Purchase #5	$70.47	9.493%	$77.1597	$77.16	$77.15	$77.20
Purchase #6	$81.69	5.211%	$85.9469	$85.95	$85.95	$85.90
Purchase #7	$145.78	12.857%	$164.5229	$164.52	$164.50	$164.50
7 purchase totals =	$627.55		$685.9366	$685.94	$685.90	$685.90