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	$206.87	7.521%	$222.4287	$222.43	$222.45	$222.40
Purchase #2	$12.72	8.319%	$13.7782	$13.78	$13.80	$13.80
Purchase #3	$186.90	7.858%	$201.5866	$201.59	$201.60	$201.60
Purchase #4	$74.30	10.196%	$81.8756	$81.88	$81.90	$81.90
Purchase #5	$22.58	12.512%	$25.4052	$25.41	$25.40	$25.40
Purchase #6	$223.25	13.724%	$253.8888	$253.89	$253.90	$253.90
Purchase #7	$191.87	13.508%	$217.7878	$217.79	$217.80	$217.80
7 purchase totals =	$918.49		$1,016.7509	$1,016.77	$1,016.85	$1,016.80