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 $182.59   7.783%   $196.801   $196.80   $196.80   $196.80  
  Purchase #2 $221.85   6.243%   $235.7001   $235.70   $235.70   $235.70  
  Purchase #3 $167.63   11.372%   $186.6929   $186.69   $186.70   $186.70  
  Purchase #4 $25.54   12.370%   $28.6993   $28.70   $28.70   $28.70  
  Purchase #5 $73.74   12.688%   $83.0961   $83.10   $83.10   $83.10  
  Purchase #6 $238.82   12.180%   $267.9083   $267.91   $267.90   $267.90  
  Purchase #7 $47.89   12.468%   $53.8609   $53.86   $53.85   $53.90  
  7 purchase totals = $958.06       $1,052.7586   $1,052.76   $1,052.75   $1,052.80