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 $59.83   5.392%   $63.056   $63.06   $63.05   $63.10  
  Purchase #2 $70.74   7.439%   $76.0023   $76.00   $76.00   $76.00  
  Purchase #3 $65.41   12.441%   $73.5477   $73.55   $73.55   $73.50  
  Purchase #4 $201.70   12.361%   $226.6321   $226.63   $226.65   $226.60  
  Purchase #5 $125.37   6.361%   $133.3448   $133.34   $133.35   $133.30  
  Purchase #6 $146.66   6.764%   $156.5801   $156.58   $156.60   $156.60  
  Purchase #7 $22.25   6.687%   $23.7379   $23.74   $23.75   $23.70  
  7 purchase totals = $691.96       $752.9009   $752.90   $752.95   $752.80