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	$107.89	10.176%	$118.8689	$118.87	$118.85	$118.90
Purchase #2	$90.70	12.646%	$102.1699	$102.17	$102.15	$102.20
Purchase #3	$170.44	8.836%	$185.5001	$185.50	$185.50	$185.50
Purchase #4	$109.65	4.770%	$114.8803	$114.88	$114.90	$114.90
Purchase #5	$48.70	9.726%	$53.4366	$53.44	$53.45	$53.40
Purchase #6	$182.96	9.575%	$200.4784	$200.48	$200.50	$200.50
Purchase #7	$231.42	12.815%	$261.0765	$261.08	$261.10	$261.10
7 purchase totals =	$941.76		$1,036.4107	$1,036.42	$1,036.45	$1,036.50