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 $88.39   6.506%   $94.1407   $94.14   $94.15   $94.10  
  Purchase #2 $127.87   4.292%   $133.3582   $133.36   $133.35   $133.40  
  Purchase #3 $42.72   5.233%   $44.9555   $44.96   $44.95   $45.00  
  Purchase #4 $242.81   7.669%   $261.4311   $261.43   $261.45   $261.40  
  Purchase #5 $160.42   13.842%   $182.6253   $182.63   $182.65   $182.60  
  Purchase #6 $49.45   12.508%   $55.6352   $55.64   $55.65   $55.60  
  Purchase #7 $14.65   3.759%   $15.2007   $15.20   $15.20   $15.20  
  7 purchase totals = $726.31       $787.3467   $787.36   $787.40   $787.30