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 $58.71   6.213%   $62.3577   $62.36   $62.35   $62.40  
  Purchase #2 $59.95   3.525%   $62.0632   $62.06   $62.05   $62.10  
  Purchase #3 $170.61   13.759%   $194.0842   $194.08   $194.10   $194.10  
  Purchase #4 $30.95   5.216%   $32.5644   $32.56   $32.55   $32.60  
  Purchase #5 $60.62   12.481%   $68.186   $68.19   $68.20   $68.20  
  Purchase #6 $193.96   11.734%   $216.7193   $216.72   $216.70   $216.70  
  Purchase #7 $85.63   13.217%   $96.9477   $96.95   $96.95   $96.90  
  7 purchase totals = $660.43       $732.9225   $732.92   $732.90   $733.00