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	$222.81	9.599%	$244.1975	$244.20	$244.20	$244.20
Purchase #2	$57.83	8.242%	$62.5963	$62.60	$62.60	$62.60
Purchase #3	$87.54	5.619%	$92.4589	$92.46	$92.45	$92.50
Purchase #4	$111.61	6.727%	$119.118	$119.12	$119.10	$119.10
Purchase #5	$107.75	3.221%	$111.2206	$111.22	$111.20	$111.20
Purchase #6	$181.82	9.371%	$198.8584	$198.86	$198.85	$198.90
Purchase #7	$204.38	8.375%	$221.4968	$221.50	$221.50	$221.50
7 purchase totals =	$973.74		$1,049.9465	$1,049.96	$1,049.90	$1,050.00