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	$200.50	11.108%	$222.7715	$222.77	$222.75	$222.80
Purchase #2	$34.51	11.131%	$38.3513	$38.35	$38.35	$38.40
Purchase #3	$112.99	9.159%	$123.3388	$123.34	$123.35	$123.30
Purchase #4	$39.90	12.227%	$44.7786	$44.78	$44.80	$44.80
Purchase #5	$216.45	9.215%	$236.3959	$236.40	$236.40	$236.40
Purchase #6	$178.69	5.696%	$188.8682	$188.87	$188.85	$188.90
Purchase #7	$169.93	10.105%	$187.1014	$187.10	$187.10	$187.10
7 purchase totals =	$952.97		$1,041.6057	$1,041.61	$1,041.60	$1,041.70