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	$195.38	5.327%	$205.7879	$205.79	$205.80	$205.80
Purchase #2	$122.56	12.430%	$137.7942	$137.79	$137.80	$137.80
Purchase #3	$100.60	8.794%	$109.4468	$109.45	$109.45	$109.40
Purchase #4	$226.81	5.263%	$238.747	$238.75	$238.75	$238.70
Purchase #5	$169.83	10.360%	$187.4244	$187.42	$187.40	$187.40
Purchase #6	$146.40	8.334%	$158.601	$158.60	$158.60	$158.60
Purchase #7	$194.70	11.753%	$217.5831	$217.58	$217.60	$217.60
7 purchase totals =	$1,156.28		$1,255.3844	$1,255.38	$1,255.40	$1,255.30