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	$133.35	6.715%	$142.3045	$142.30	$142.30	$142.30
Purchase #2	$107.83	4.176%	$112.333	$112.33	$112.35	$112.30
Purchase #3	$162.85	5.627%	$172.0136	$172.01	$172.00	$172.00
Purchase #4	$159.79	10.677%	$176.8508	$176.85	$176.85	$176.90
Purchase #5	$165.85	6.480%	$176.5971	$176.60	$176.60	$176.60
Purchase #6	$96.47	13.477%	$109.4713	$109.47	$109.45	$109.50
Purchase #7	$225.71	8.725%	$245.4032	$245.40	$245.40	$245.40
7 purchase totals =	$1,051.85		$1,134.9735	$1,134.96	$1,134.95	$1,135.00