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	$219.96	8.313%	$238.2453	$238.25	$238.25	$238.20
Purchase #2	$86.58	12.409%	$97.3237	$97.32	$97.30	$97.30
Purchase #3	$44.55	5.211%	$46.8715	$46.87	$46.85	$46.90
Purchase #4	$186.56	5.334%	$196.5111	$196.51	$196.50	$196.50
Purchase #5	$184.79	3.493%	$191.2447	$191.24	$191.25	$191.20
Purchase #6	$39.50	10.382%	$43.6009	$43.60	$43.60	$43.60
Purchase #7	$21.35	5.815%	$22.5915	$22.59	$22.60	$22.60
7 purchase totals =	$783.29		$836.3887	$836.38	$836.35	$836.30