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	$141.66	11.146%	$157.4494	$157.45	$157.45	$157.40
Purchase #2	$74.77	4.336%	$78.012	$78.01	$78.00	$78.00
Purchase #3	$125.58	9.487%	$137.4938	$137.49	$137.50	$137.50
Purchase #4	$163.51	4.508%	$170.881	$170.88	$170.90	$170.90
Purchase #5	$208.41	6.810%	$222.6027	$222.60	$222.60	$222.60
Purchase #6	$189.94	9.563%	$208.104	$208.10	$208.10	$208.10
Purchase #7	$62.89	7.213%	$67.4263	$67.43	$67.45	$67.40
7 purchase totals =	$966.76		$1,041.9692	$1,041.96	$1,042.00	$1,041.90