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 $87.51   7.839%   $94.3699   $94.37   $94.35   $94.40  
  Purchase #2 $210.51   4.372%   $219.7135   $219.71   $219.70   $219.70  
  Purchase #3 $57.73   9.177%   $63.0279   $63.03   $63.05   $63.00  
  Purchase #4 $191.51   5.692%   $202.4107   $202.41   $202.40   $202.40  
  Purchase #5 $208.41   6.508%   $221.9733   $221.97   $221.95   $222.00  
  Purchase #6 $78.65   13.800%   $89.5037   $89.50   $89.50   $89.50  
  Purchase #7 $128.25   3.781%   $133.0991   $133.10   $133.10   $133.10  
  7 purchase totals = $962.57       $1,024.0981   $1,024.09   $1,024.05   $1,024.10