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 $58.66   10.230%   $64.6609   $64.66   $64.65   $64.70  
  Purchase #2 $60.54   11.665%   $67.602   $67.60   $67.60   $67.60  
  Purchase #3 $28.49   7.619%   $30.6607   $30.66   $30.65   $30.70  
  Purchase #4 $10.81   10.364%   $11.9303   $11.93   $11.95   $11.90  
  Purchase #5 $24.47   6.813%   $26.1371   $26.14   $26.15   $26.10  
  Purchase #6 $47.45   8.487%   $51.4771   $51.48   $51.50   $51.50  
  Purchase #7 $35.73   10.126%   $39.348   $39.35   $39.35   $39.30  
  7 purchase totals = $266.15       $291.8161   $291.82   $291.85   $291.80