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	$37.55	10.169%	$41.3685	$41.37	$41.35	$41.40
Purchase #2	$82.89	8.682%	$90.0865	$90.09	$90.10	$90.10
Purchase #3	$119.76	7.116%	$128.2821	$128.28	$128.30	$128.30
Purchase #4	$5.82	3.215%	$6.0071	$6.01	$6.00	$6.00
Purchase #5	$250.95	10.669%	$277.7239	$277.72	$277.70	$277.70
Purchase #6	$241.80	8.377%	$262.0556	$262.06	$262.05	$262.10
Purchase #7	$144.76	7.715%	$155.9282	$155.93	$155.95	$155.90
7 purchase totals =	$883.53		$961.4519	$961.46	$961.45	$961.50