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	$182.53	8.136%	$197.3806	$197.38	$197.40	$197.40
Purchase #2	$137.81	10.718%	$152.5805	$152.58	$152.60	$152.60
Purchase #3	$18.41	13.233%	$20.8462	$20.85	$20.85	$20.80
Purchase #4	$106.87	12.699%	$120.4414	$120.44	$120.45	$120.40
Purchase #5	$171.94	12.156%	$192.841	$192.84	$192.85	$192.80
Purchase #6	$61.69	9.492%	$67.5456	$67.55	$67.55	$67.50
Purchase #7	$177.72	7.286%	$190.6687	$190.67	$190.65	$190.70
7 purchase totals =	$856.97		$942.3040	$942.31	$942.35	$942.20