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	$107.88	3.254%	$111.3904	$111.39	$111.40	$111.40
Purchase #2	$158.29	4.193%	$164.9271	$164.93	$164.95	$164.90
Purchase #3	$111.53	7.230%	$119.5936	$119.59	$119.60	$119.60
Purchase #4	$76.65	7.527%	$82.4194	$82.42	$82.40	$82.40
Purchase #5	$125.98	6.174%	$133.758	$133.76	$133.75	$133.80
Purchase #6	$225.98	9.129%	$246.6097	$246.61	$246.60	$246.60
Purchase #7	$23.92	3.702%	$24.8055	$24.81	$24.80	$24.80
7 purchase totals =	$830.23		$883.5037	$883.51	$883.50	$883.50