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 $86.87   9.794%   $95.378   $95.38   $95.40   $95.40  
  Purchase #2 $152.74   13.628%   $173.5554   $173.56   $173.55   $173.60  
  Purchase #3 $81.87   3.426%   $84.6749   $84.67   $84.65   $84.70  
  Purchase #4 $69.69   13.441%   $79.057   $79.06   $79.05   $79.10  
  Purchase #5 $131.29   7.662%   $141.3494   $141.35   $141.35   $141.30  
  Purchase #6 $72.32   12.282%   $81.2023   $81.20   $81.20   $81.20  
  Purchase #7 $48.29   13.780%   $54.9444   $54.94   $54.95   $54.90  
  7 purchase totals = $643.07       $710.1614   $710.16   $710.15   $710.20