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	$78.40	11.447%	$87.3744	$87.37	$87.35	$87.40
Purchase #2	$120.76	8.585%	$131.1272	$131.13	$131.15	$131.10
Purchase #3	$226.89	4.678%	$237.5039	$237.50	$237.50	$237.50
Purchase #4	$25.59	12.142%	$28.6971	$28.70	$28.70	$28.70
Purchase #5	$185.53	5.223%	$195.2202	$195.22	$195.20	$195.20
Purchase #6	$91.45	9.839%	$100.4478	$100.45	$100.45	$100.40
Purchase #7	$116.42	3.836%	$120.8859	$120.89	$120.90	$120.90
7 purchase totals =	$845.04		$901.2565	$901.26	$901.25	$901.20