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	$104.50	11.587%	$116.6084	$116.61	$116.60	$116.60
Purchase #2	$41.80	10.155%	$46.0448	$46.04	$46.05	$46.00
Purchase #3	$18.49	9.601%	$20.2652	$20.27	$20.25	$20.30
Purchase #4	$100.62	9.589%	$110.2685	$110.27	$110.25	$110.30
Purchase #5	$18.53	4.550%	$19.3731	$19.37	$19.35	$19.40
Purchase #6	$142.96	5.204%	$150.3996	$150.40	$150.40	$150.40
Purchase #7	$205.86	12.418%	$231.4237	$231.42	$231.40	$231.40
7 purchase totals =	$632.76		$694.3833	$694.38	$694.30	$694.40