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	$233.31	7.706%	$251.2889	$251.29	$251.30	$251.30
Purchase #2	$179.59	9.142%	$196.0081	$196.01	$196.00	$196.00
Purchase #3	$43.43	5.546%	$45.8386	$45.84	$45.85	$45.80
Purchase #4	$81.57	11.490%	$90.9424	$90.94	$90.95	$90.90
Purchase #5	$36.64	13.726%	$41.6692	$41.67	$41.65	$41.70
Purchase #6	$180.45	12.411%	$202.8456	$202.85	$202.85	$202.80
Purchase #7	$200.82	6.180%	$213.2307	$213.23	$213.25	$213.20
7 purchase totals =	$955.81		$1,041.8235	$1,041.83	$1,041.85	$1,041.70