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 $53.48   8.370%   $57.9563   $57.96   $57.95   $58.00  
  Purchase #2 $244.32   9.338%   $267.1346   $267.13   $267.15   $267.10  
  Purchase #3 $235.96   7.302%   $253.1898   $253.19   $253.20   $253.20  
  Purchase #4 $229.45   3.600%   $237.7102   $237.71   $237.70   $237.70  
  Purchase #5 $63.55   5.355%   $66.9531   $66.95   $66.95   $67.00  
  Purchase #6 $72.83   5.563%   $76.8815   $76.88   $76.90   $76.90  
  Purchase #7 $39.68   3.642%   $41.1251   $41.13   $41.15   $41.10  
  7 purchase totals = $939.27       $1,000.9506   $1,000.95   $1,001.00   $1,001.00