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	$13.71	5.776%	$14.5019	$14.50	$14.50	$14.50
Purchase #2	$166.88	5.738%	$176.4556	$176.46	$176.45	$176.50
Purchase #3	$160.86	4.299%	$167.7754	$167.78	$167.80	$167.80
Purchase #4	$145.87	3.843%	$151.4758	$151.48	$151.50	$151.50
Purchase #5	$16.89	9.724%	$18.5324	$18.53	$18.55	$18.50
Purchase #6	$140.49	13.648%	$159.6641	$159.66	$159.65	$159.70
Purchase #7	$229.31	5.124%	$241.0598	$241.06	$241.05	$241.10
7 purchase totals =	$874.01		$929.4650	$929.47	$929.50	$929.60