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	$219.56	8.717%	$238.699	$238.70	$238.70	$238.70
Purchase #2	$60.27	3.504%	$62.3819	$62.38	$62.40	$62.40
Purchase #3	$204.39	7.198%	$219.102	$219.10	$219.10	$219.10
Purchase #4	$38.65	7.348%	$41.49	$41.49	$41.50	$41.50
Purchase #5	$130.48	4.650%	$136.5473	$136.55	$136.55	$136.50
Purchase #6	$227.43	5.789%	$240.5959	$240.60	$240.60	$240.60
Purchase #7	$172.85	6.750%	$184.5174	$184.52	$184.50	$184.50
7 purchase totals =	$1,053.63		$1,123.3335	$1,123.34	$1,123.35	$1,123.30