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 $90.29   4.774%   $94.6004   $94.60   $94.60   $94.60  
  Purchase #2 $110.66   3.659%   $114.709   $114.71   $114.70   $114.70  
  Purchase #3 $135.76   13.581%   $154.1976   $154.20   $154.20   $154.20  
  Purchase #4 $244.43   6.151%   $259.4649   $259.46   $259.45   $259.50  
  Purchase #5 $39.69   8.327%   $42.995   $43.00   $43.00   $43.00  
  Purchase #6 $128.68   8.173%   $139.197   $139.20   $139.20   $139.20  
  Purchase #7 $230.80   11.357%   $257.012   $257.01   $257.00   $257.00  
  7 purchase totals = $980.31       $1,062.1759   $1,062.18   $1,062.15   $1,062.20