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	$112.81	5.669%	$119.2052	$119.21	$119.20	$119.20
Purchase #2	$44.50	6.233%	$47.2737	$47.27	$47.25	$47.30
Purchase #3	$62.55	12.222%	$70.1949	$70.19	$70.20	$70.20
Purchase #4	$160.46	7.575%	$172.6148	$172.61	$172.60	$172.60
Purchase #5	$209.27	7.613%	$225.2017	$225.20	$225.20	$225.20
Purchase #6	$155.56	10.783%	$172.334	$172.33	$172.35	$172.30
Purchase #7	$131.92	3.491%	$136.5253	$136.53	$136.55	$136.50
7 purchase totals =	$877.07		$943.3496	$943.34	$943.35	$943.30