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	$83.81	8.493%	$90.928	$90.93	$90.95	$90.90
Purchase #2	$113.87	11.440%	$126.8967	$126.90	$126.90	$126.90
Purchase #3	$177.39	6.853%	$189.5465	$189.55	$189.55	$189.50
Purchase #4	$191.29	12.500%	$215.2013	$215.20	$215.20	$215.20
Purchase #5	$77.67	5.370%	$81.8409	$81.84	$81.85	$81.80
Purchase #6	$215.45	12.488%	$242.3554	$242.36	$242.35	$242.40
Purchase #7	$225.77	10.796%	$250.1441	$250.14	$250.15	$250.10
7 purchase totals =	$1,085.25		$1,196.9129	$1,196.92	$1,196.95	$1,196.80