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 $84.29   11.591%   $94.0601   $94.06   $94.05   $94.10  
  Purchase #2 $246.91   4.748%   $258.6333   $258.63   $258.65   $258.60  
  Purchase #3 $10.25   4.543%   $10.7157   $10.72   $10.70   $10.70  
  Purchase #4 $93.83   4.461%   $98.0158   $98.02   $98.00   $98.00  
  Purchase #5 $28.99   12.638%   $32.6538   $32.65   $32.65   $32.70  
  Purchase #6 $214.71   8.314%   $232.561   $232.56   $232.55   $232.60  
  Purchase #7 $56.87   3.701%   $58.9748   $58.97   $58.95   $59.00  
  7 purchase totals = $735.85       $785.6145   $785.61   $785.55   $785.70