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	$166.94	3.317%	$172.4774	$172.48	$172.50	$172.50
Purchase #2	$126.90	3.768%	$131.6816	$131.68	$131.70	$131.70
Purchase #3	$211.32	8.287%	$228.8321	$228.83	$228.85	$228.80
Purchase #4	$190.38	12.738%	$214.6306	$214.63	$214.65	$214.60
Purchase #5	$241.27	9.136%	$263.3124	$263.31	$263.30	$263.30
Purchase #6	$221.86	12.568%	$249.7434	$249.74	$249.75	$249.70
Purchase #7	$136.74	5.181%	$143.8245	$143.82	$143.80	$143.80
7 purchase totals =	$1,295.41		$1,404.5020	$1,404.49	$1,404.55	$1,404.40