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 $58.28   7.701%   $62.7681   $62.77   $62.75   $62.80  
  Purchase #2 $185.61   8.635%   $201.6374   $201.64   $201.65   $201.60  
  Purchase #3 $32.63   12.682%   $36.7681   $36.77   $36.75   $36.80  
  Purchase #4 $54.27   13.447%   $61.5677   $61.57   $61.55   $61.60  
  Purchase #5 $226.46   8.666%   $246.085   $246.09   $246.10   $246.10  
  Purchase #6 $242.32   5.519%   $255.6936   $255.69   $255.70   $255.70  
  Purchase #7 $59.75   11.618%   $66.6918   $66.69   $66.70   $66.70  
  7 purchase totals = $859.32       $931.2117   $931.22   $931.20   $931.30