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	$121.54	8.157%	$131.454	$131.45	$131.45	$131.50
Purchase #2	$116.60	10.141%	$128.4244	$128.42	$128.40	$128.40
Purchase #3	$50.57	11.824%	$56.5494	$56.55	$56.55	$56.50
Purchase #4	$102.60	6.476%	$109.2444	$109.24	$109.25	$109.20
Purchase #5	$127.30	10.250%	$140.3483	$140.35	$140.35	$140.30
Purchase #6	$217.77	3.643%	$225.7034	$225.70	$225.70	$225.70
Purchase #7	$208.81	3.205%	$215.5024	$215.50	$215.50	$215.50
7 purchase totals =	$945.19		$1,007.2263	$1,007.21	$1,007.20	$1,007.10