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	$143.86	11.590%	$160.5334	$160.53	$160.55	$160.50
Purchase #2	$196.79	5.734%	$208.0739	$208.07	$208.05	$208.10
Purchase #3	$113.84	4.209%	$118.6315	$118.63	$118.65	$118.60
Purchase #4	$75.33	13.411%	$85.4325	$85.43	$85.45	$85.40
Purchase #5	$52.89	12.727%	$59.6213	$59.62	$59.60	$59.60
Purchase #6	$67.47	13.661%	$76.6871	$76.69	$76.70	$76.70
Purchase #7	$88.58	9.693%	$97.1661	$97.17	$97.15	$97.20
7 purchase totals =	$738.76		$806.1458	$806.14	$806.15	$806.10