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 $119.82   3.372%   $123.8603   $123.86   $123.85   $123.90  
  Purchase #2 $182.48   10.156%   $201.0127   $201.01   $201.00   $201.00  
  Purchase #3 $75.36   7.599%   $81.0866   $81.09   $81.10   $81.10  
  Purchase #4 $245.53   6.284%   $260.9591   $260.96   $260.95   $261.00  
  Purchase #5 $238.59   10.173%   $262.8618   $262.86   $262.85   $262.90  
  Purchase #6 $46.74   11.353%   $52.0464   $52.05   $52.05   $52.00  
  Purchase #7 $154.73   6.570%   $164.8958   $164.90   $164.90   $164.90  
  7 purchase totals = $1,063.25       $1,146.7227   $1,146.73   $1,146.70   $1,146.80