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	$132.82	11.813%	$148.51	$148.51	$148.50	$148.50
Purchase #2	$64.88	11.395%	$72.2731	$72.27	$72.25	$72.30
Purchase #3	$215.69	4.504%	$225.4047	$225.40	$225.40	$225.40
Purchase #4	$105.84	9.641%	$116.044	$116.04	$116.05	$116.00
Purchase #5	$172.86	10.398%	$190.834	$190.83	$190.85	$190.80
Purchase #6	$184.51	11.104%	$204.998	$205.00	$205.00	$205.00
Purchase #7	$191.38	3.546%	$198.1663	$198.17	$198.15	$198.20
7 purchase totals =	$1,067.98		$1,156.2301	$1,156.22	$1,156.20	$1,156.20