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 $95.25   7.451%   $102.3471   $102.35   $102.35   $102.30  
  Purchase #2 $183.59   13.265%   $207.9432   $207.94   $207.95   $207.90  
  Purchase #3 $25.66   11.211%   $28.5367   $28.54   $28.55   $28.50  
  Purchase #4 $182.65   10.340%   $201.536   $201.54   $201.55   $201.50  
  Purchase #5 $98.49   5.280%   $103.6903   $103.69   $103.70   $103.70  
  Purchase #6 $20.87   11.749%   $23.322   $23.32   $23.30   $23.30  
  Purchase #7 $219.85   8.303%   $238.1041   $238.10   $238.10   $238.10  
  7 purchase totals = $826.36       $905.4794   $905.48   $905.50   $905.30