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 $181.60   7.216%   $194.7043   $194.70   $194.70   $194.70  
  Purchase #2 $16.95   13.853%   $19.2981   $19.30   $19.30   $19.30  
  Purchase #3 $226.72   5.689%   $239.6181   $239.62   $239.60   $239.60  
  Purchase #4 $125.86   7.704%   $135.5563   $135.56   $135.55   $135.60  
  Purchase #5 $154.59   13.767%   $175.8724   $175.87   $175.85   $175.90  
  Purchase #6 $95.76   8.706%   $104.0969   $104.10   $104.10   $104.10  
  Purchase #7 $135.94   5.189%   $142.9939   $142.99   $143.00   $143.00  
  7 purchase totals = $937.42       $1,012.1400   $1,012.14   $1,012.10   $1,012.20