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 $76.75   11.185%   $85.3345   $85.33   $85.35   $85.30  
  Purchase #2 $159.84   12.457%   $179.7513   $179.75   $179.75   $179.80  
  Purchase #3 $187.30   11.182%   $208.2439   $208.24   $208.25   $208.20  
  Purchase #4 $230.65   4.359%   $240.704   $240.70   $240.70   $240.70  
  Purchase #5 $173.49   11.510%   $193.4587   $193.46   $193.45   $193.50  
  Purchase #6 $129.48   8.380%   $140.3304   $140.33   $140.35   $140.30  
  Purchase #7 $166.53   8.351%   $180.4369   $180.44   $180.45   $180.40  
  7 purchase totals = $1,124.04       $1,228.2597   $1,228.25   $1,228.30   $1,228.20