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	$139.52	10.590%	$154.2952	$154.30	$154.30	$154.30
Purchase #2	$133.46	11.418%	$148.6985	$148.70	$148.70	$148.70
Purchase #3	$63.39	5.162%	$66.6622	$66.66	$66.65	$66.70
Purchase #4	$89.96	6.240%	$95.5735	$95.57	$95.55	$95.60
Purchase #5	$199.35	8.639%	$216.5718	$216.57	$216.55	$216.60
Purchase #6	$78.67	4.718%	$82.3817	$82.38	$82.40	$82.40
Purchase #7	$129.69	3.741%	$134.5417	$134.54	$134.55	$134.50
7 purchase totals =	$834.04		$898.7246	$898.72	$898.70	$898.80