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 $211.50   11.541%   $235.9092   $235.91   $235.90   $235.90  
  Purchase #2 $97.40   12.834%   $109.9003   $109.90   $109.90   $109.90  
  Purchase #3 $201.66   12.106%   $226.073   $226.07   $226.05   $226.10  
  Purchase #4 $48.30   8.782%   $52.5417   $52.54   $52.55   $52.50  
  Purchase #5 $44.89   12.139%   $50.3392   $50.34   $50.35   $50.30  
  Purchase #6 $220.64   12.244%   $247.6552   $247.66   $247.65   $247.70  
  Purchase #7 $91.55   12.788%   $103.2574   $103.26   $103.25   $103.30  
  7 purchase totals = $915.94       $1,025.6760   $1,025.68   $1,025.65   $1,025.70