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	$233.33	12.641%	$262.8252	$262.83	$262.85	$262.80
Purchase #2	$85.75	11.280%	$95.4226	$95.42	$95.40	$95.40
Purchase #3	$145.33	13.244%	$164.5775	$164.58	$164.60	$164.60
Purchase #4	$92.54	4.289%	$96.509	$96.51	$96.50	$96.50
Purchase #5	$81.53	3.746%	$84.5841	$84.58	$84.60	$84.60
Purchase #6	$19.76	9.248%	$21.5874	$21.59	$21.60	$21.60
Purchase #7	$185.48	4.527%	$193.8767	$193.88	$193.90	$193.90
7 purchase totals =	$843.72		$919.3825	$919.39	$919.45	$919.40