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 $64.83   6.387%   $68.9707   $68.97   $68.95   $69.00  
  Purchase #2 $189.49   7.293%   $203.3095   $203.31   $203.30   $203.30  
  Purchase #3 $30.70   13.620%   $34.8813   $34.88   $34.90   $34.90  
  Purchase #4 $185.94   8.266%   $201.3098   $201.31   $201.30   $201.30  
  Purchase #5 $167.56   12.679%   $188.8049   $188.80   $188.80   $188.80  
  Purchase #6 $138.76   13.102%   $156.9403   $156.94   $156.95   $156.90  
  Purchase #7 $141.65   12.790%   $159.767   $159.77   $159.75   $159.80  
  7 purchase totals = $918.93       $1,013.9835   $1,013.98   $1,013.95   $1,014.00