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 $184.93   5.680%   $195.434   $195.43   $195.45   $195.40  
  Purchase #2 $146.51   10.842%   $162.3946   $162.39   $162.40   $162.40  
  Purchase #3 $70.46   3.169%   $72.6929   $72.69   $72.70   $72.70  
  Purchase #4 $221.40   8.715%   $240.695   $240.70   $240.70   $240.70  
  Purchase #5 $58.48   12.701%   $65.9075   $65.91   $65.90   $65.90  
  Purchase #6 $168.86   11.394%   $188.0999   $188.10   $188.10   $188.10  
  Purchase #7 $103.81   3.523%   $107.4672   $107.47   $107.45   $107.50  
  7 purchase totals = $954.45       $1,032.6911   $1,032.69   $1,032.70   $1,032.70