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	$142.60	10.829%	$158.0422	$158.04	$158.05	$158.00
Purchase #2	$73.57	10.494%	$81.2904	$81.29	$81.30	$81.30
Purchase #3	$191.65	13.763%	$218.0268	$218.03	$218.05	$218.00
Purchase #4	$142.66	7.126%	$152.826	$152.83	$152.85	$152.80
Purchase #5	$225.64	13.258%	$255.5554	$255.56	$255.55	$255.60
Purchase #6	$49.34	6.539%	$52.5663	$52.57	$52.55	$52.60
Purchase #7	$117.53	3.150%	$121.2322	$121.23	$121.25	$121.20
7 purchase totals =	$942.99		$1,039.5393	$1,039.55	$1,039.60	$1,039.50