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	$95.37	13.611%	$108.3508	$108.35	$108.35	$108.40
Purchase #2	$236.90	11.838%	$264.9442	$264.94	$264.95	$264.90
Purchase #3	$235.39	10.401%	$259.8729	$259.87	$259.85	$259.90
Purchase #4	$160.87	8.193%	$174.0501	$174.05	$174.05	$174.10
Purchase #5	$81.94	10.113%	$90.2266	$90.23	$90.25	$90.20
Purchase #6	$164.28	7.185%	$176.0835	$176.08	$176.10	$176.10
Purchase #7	$28.93	9.218%	$31.5968	$31.60	$31.60	$31.60
7 purchase totals =	$1,003.68		$1,105.1249	$1,105.12	$1,105.15	$1,105.20