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	$169.40	10.473%	$187.1413	$187.14	$187.15	$187.10
Purchase #2	$156.26	5.290%	$164.5262	$164.53	$164.55	$164.50
Purchase #3	$97.74	13.864%	$111.2907	$111.29	$111.30	$111.30
Purchase #4	$241.54	8.207%	$261.3632	$261.36	$261.35	$261.40
Purchase #5	$236.34	5.523%	$249.3931	$249.39	$249.40	$249.40
Purchase #6	$108.81	13.433%	$123.4264	$123.43	$123.45	$123.40
Purchase #7	$215.58	4.544%	$225.376	$225.38	$225.40	$225.40
7 purchase totals =	$1,225.67		$1,322.5169	$1,322.52	$1,322.60	$1,322.50