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	$24.41	3.346%	$25.2268	$25.23	$25.25	$25.20
Purchase #2	$95.52	6.792%	$102.0077	$102.01	$102.00	$102.00
Purchase #3	$157.87	8.467%	$171.2369	$171.24	$171.25	$171.20
Purchase #4	$41.35	11.342%	$46.0399	$46.04	$46.05	$46.00
Purchase #5	$68.46	10.142%	$75.4032	$75.40	$75.40	$75.40
Purchase #6	$96.86	9.242%	$105.8118	$105.81	$105.80	$105.80
Purchase #7	$71.41	10.405%	$78.8402	$78.84	$78.85	$78.80
7 purchase totals =	$555.88		$604.5665	$604.57	$604.60	$604.40