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	$59.55	13.103%	$67.3528	$67.35	$67.35	$67.40
Purchase #2	$201.60	3.359%	$208.3717	$208.37	$208.35	$208.40
Purchase #3	$174.95	6.622%	$186.5352	$186.54	$186.55	$186.50
Purchase #4	$119.85	6.196%	$127.2759	$127.28	$127.30	$127.30
Purchase #5	$52.57	5.407%	$55.4125	$55.41	$55.40	$55.40
Purchase #6	$42.94	10.301%	$47.3632	$47.36	$47.35	$47.40
Purchase #7	$225.38	10.762%	$249.6354	$249.64	$249.65	$249.60
7 purchase totals =	$876.84		$941.9467	$941.95	$941.95	$942.00