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	$115.62	12.467%	$130.0343	$130.03	$130.05	$130.00
Purchase #2	$102.66	8.627%	$111.5165	$111.52	$111.50	$111.50
Purchase #3	$135.47	4.369%	$141.3887	$141.39	$141.40	$141.40
Purchase #4	$109.46	10.572%	$121.0321	$121.03	$121.05	$121.00
Purchase #5	$155.56	8.570%	$168.8915	$168.89	$168.90	$168.90
Purchase #6	$202.43	5.397%	$213.3551	$213.36	$213.35	$213.40
Purchase #7	$193.81	9.819%	$212.8402	$212.84	$212.85	$212.80
7 purchase totals =	$1,015.01		$1,099.0584	$1,099.06	$1,099.10	$1,099.00