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	$142.27	13.583%	$161.5945	$161.59	$161.60	$161.60
Purchase #2	$154.56	7.705%	$166.4688	$166.47	$166.45	$166.50
Purchase #3	$12.77	8.554%	$13.8623	$13.86	$13.85	$13.90
Purchase #4	$155.54	7.117%	$166.6098	$166.61	$166.60	$166.60
Purchase #5	$166.57	6.493%	$177.3854	$177.39	$177.40	$177.40
Purchase #6	$199.61	8.483%	$216.5429	$216.54	$216.55	$216.50
Purchase #7	$221.96	3.814%	$230.4256	$230.43	$230.45	$230.40
7 purchase totals =	$1,053.28		$1,132.8893	$1,132.89	$1,132.90	$1,132.90