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 $58.89   6.351%   $62.6301   $62.63   $62.65   $62.60  
  Purchase #2 $207.26   11.174%   $230.4192   $230.42   $230.40   $230.40  
  Purchase #3 $197.40   9.719%   $216.5853   $216.59   $216.60   $216.60  
  Purchase #4 $155.71   12.653%   $175.412   $175.41   $175.40   $175.40  
  Purchase #5 $63.83   10.754%   $70.6943   $70.69   $70.70   $70.70  
  Purchase #6 $36.46   12.408%   $40.984   $40.98   $41.00   $41.00  
  Purchase #7 $229.80   9.753%   $252.2124   $252.21   $252.20   $252.20  
  7 purchase totals = $949.35       $1,048.9373   $1,048.93   $1,048.95   $1,048.90