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	$23.49	8.517%	$25.4906	$25.49	$25.50	$25.50
Purchase #2	$115.86	4.839%	$121.4665	$121.47	$121.45	$121.50
Purchase #3	$71.31	9.775%	$78.2806	$78.28	$78.30	$78.30
Purchase #4	$247.50	3.187%	$255.3878	$255.39	$255.40	$255.40
Purchase #5	$141.84	6.325%	$150.8114	$150.81	$150.80	$150.80
Purchase #6	$175.35	5.822%	$185.5589	$185.56	$185.55	$185.60
Purchase #7	$48.85	5.254%	$51.4166	$51.42	$51.40	$51.40
7 purchase totals =	$824.20		$868.4124	$868.42	$868.40	$868.50