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	$178.60	5.137%	$187.7747	$187.77	$187.75	$187.80
Purchase #2	$42.81	10.846%	$47.4532	$47.45	$47.45	$47.50
Purchase #3	$186.79	12.376%	$209.9071	$209.91	$209.90	$209.90
Purchase #4	$159.91	13.861%	$182.0751	$182.08	$182.10	$182.10
Purchase #5	$81.88	10.691%	$90.6338	$90.63	$90.65	$90.60
Purchase #6	$228.27	5.522%	$240.8751	$240.88	$240.90	$240.90
Purchase #7	$105.96	6.155%	$112.4818	$112.48	$112.50	$112.50
7 purchase totals =	$984.22		$1,071.2008	$1,071.20	$1,071.25	$1,071.30