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	$157.88	11.797%	$176.5051	$176.51	$176.50	$176.50
Purchase #2	$147.33	11.467%	$164.2243	$164.22	$164.20	$164.20
Purchase #3	$47.93	13.561%	$54.4298	$54.43	$54.45	$54.40
Purchase #4	$24.86	13.214%	$28.145	$28.15	$28.15	$28.10
Purchase #5	$215.29	5.496%	$227.1223	$227.12	$227.10	$227.10
Purchase #6	$119.57	9.766%	$131.2472	$131.25	$131.25	$131.20
Purchase #7	$169.34	8.621%	$183.9388	$183.94	$183.95	$183.90
7 purchase totals =	$882.20		$965.6125	$965.62	$965.60	$965.40