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	$176.80	5.373%	$186.2995	$186.30	$186.30	$186.30
Purchase #2	$93.39	9.434%	$102.2004	$102.20	$102.20	$102.20
Purchase #3	$45.88	3.260%	$47.3757	$47.38	$47.40	$47.40
Purchase #4	$24.71	4.830%	$25.9035	$25.90	$25.90	$25.90
Purchase #5	$75.40	8.856%	$82.0774	$82.08	$82.10	$82.10
Purchase #6	$99.92	11.507%	$111.4178	$111.42	$111.40	$111.40
Purchase #7	$147.66	12.835%	$166.6122	$166.61	$166.60	$166.60
7 purchase totals =	$663.76		$721.8865	$721.89	$721.90	$721.90