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	$40.87	7.420%	$43.9026	$43.90	$43.90	$43.90
Purchase #2	$181.32	4.280%	$189.0805	$189.08	$189.10	$189.10
Purchase #3	$164.94	7.241%	$176.8833	$176.88	$176.90	$176.90
Purchase #4	$78.80	9.797%	$86.52	$86.52	$86.50	$86.50
Purchase #5	$134.90	11.452%	$150.3487	$150.35	$150.35	$150.30
Purchase #6	$155.60	7.294%	$166.9495	$166.95	$166.95	$166.90
Purchase #7	$192.59	6.224%	$204.5768	$204.58	$204.60	$204.60
7 purchase totals =	$949.02		$1,018.2614	$1,018.26	$1,018.30	$1,018.20