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	$186.44	7.616%	$200.6393	$200.64	$200.65	$200.60
Purchase #2	$94.62	10.808%	$104.8465	$104.85	$104.85	$104.80
Purchase #3	$39.29	3.387%	$40.6208	$40.62	$40.60	$40.60
Purchase #4	$66.89	7.328%	$71.7917	$71.79	$71.80	$71.80
Purchase #5	$236.83	4.105%	$246.5519	$246.55	$246.55	$246.60
Purchase #6	$78.87	3.173%	$81.3725	$81.37	$81.35	$81.40
Purchase #7	$246.92	13.509%	$280.2764	$280.28	$280.30	$280.30
7 purchase totals =	$949.86		$1,026.0991	$1,026.10	$1,026.10	$1,026.10