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	$38.67	5.652%	$40.8556	$40.86	$40.85	$40.90
Purchase #2	$245.66	11.289%	$273.3926	$273.39	$273.40	$273.40
Purchase #3	$155.90	11.261%	$173.4559	$173.46	$173.45	$173.50
Purchase #4	$111.64	8.134%	$120.7208	$120.72	$120.70	$120.70
Purchase #5	$95.28	7.736%	$102.6509	$102.65	$102.65	$102.70
Purchase #6	$234.51	6.719%	$250.2667	$250.27	$250.25	$250.30
Purchase #7	$231.97	13.198%	$262.5854	$262.59	$262.60	$262.60
7 purchase totals =	$1,113.63		$1,223.9279	$1,223.94	$1,223.90	$1,224.10