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	$105.41	7.604%	$113.4254	$113.43	$113.45	$113.40
Purchase #2	$74.48	13.477%	$84.5177	$84.52	$84.50	$84.50
Purchase #3	$127.46	13.680%	$144.8965	$144.90	$144.90	$144.90
Purchase #4	$80.32	12.772%	$90.5785	$90.58	$90.60	$90.60
Purchase #5	$36.67	7.622%	$39.465	$39.47	$39.45	$39.50
Purchase #6	$138.51	4.222%	$144.3579	$144.36	$144.35	$144.40
Purchase #7	$101.39	3.304%	$104.7399	$104.74	$104.75	$104.70
7 purchase totals =	$664.24		$721.9809	$722.00	$722.00	$722.00