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	$209.86	9.705%	$230.2269	$230.23	$230.25	$230.20
Purchase #2	$100.80	6.382%	$107.2331	$107.23	$107.25	$107.20
Purchase #3	$169.39	11.166%	$188.3041	$188.30	$188.30	$188.30
Purchase #4	$138.47	13.781%	$157.5526	$157.55	$157.55	$157.60
Purchase #5	$52.70	6.572%	$56.1634	$56.16	$56.15	$56.20
Purchase #6	$28.77	10.719%	$31.8539	$31.85	$31.85	$31.90
Purchase #7	$208.60	10.807%	$231.1434	$231.14	$231.15	$231.10
7 purchase totals =	$908.59		$1,002.4774	$1,002.46	$1,002.50	$1,002.50