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	$130.60	9.539%	$143.0579	$143.06	$143.05	$143.10
Purchase #2	$133.74	10.348%	$147.5794	$147.58	$147.60	$147.60
Purchase #3	$218.81	13.811%	$249.0298	$249.03	$249.05	$249.00
Purchase #4	$171.45	7.194%	$183.7841	$183.78	$183.80	$183.80
Purchase #5	$133.40	12.770%	$150.4352	$150.44	$150.45	$150.40
Purchase #6	$128.58	8.462%	$139.4604	$139.46	$139.45	$139.50
Purchase #7	$112.58	5.293%	$118.5389	$118.54	$118.55	$118.50
7 purchase totals =	$1,029.16		$1,131.8857	$1,131.89	$1,131.95	$1,131.90