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 $59.95   4.586%   $62.6993   $62.70   $62.70   $62.70  
  Purchase #2 $110.88   13.148%   $125.4585   $125.46   $125.45   $125.50  
  Purchase #3 $132.64   7.705%   $142.8599   $142.86   $142.85   $142.90  
  Purchase #4 $181.68   7.459%   $195.2315   $195.23   $195.25   $195.20  
  Purchase #5 $222.58   6.771%   $237.6509   $237.65   $237.65   $237.70  
  Purchase #6 $155.35   12.609%   $174.9381   $174.94   $174.95   $174.90  
  Purchase #7 $80.61   11.849%   $90.1615   $90.16   $90.15   $90.20  
  7 purchase totals = $943.69       $1,028.9997   $1,029.00   $1,029.00   $1,029.10