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 $85.66   8.410%   $92.864   $92.86   $92.85   $92.90  
  Purchase #2 $185.54   6.612%   $197.8079   $197.81   $197.80   $197.80  
  Purchase #3 $126.40   4.191%   $131.6974   $131.70   $131.70   $131.70  
  Purchase #4 $174.35   5.784%   $184.4344   $184.43   $184.45   $184.40  
  Purchase #5 $213.90   7.850%   $230.6912   $230.69   $230.70   $230.70  
  Purchase #6 $237.60   13.733%   $270.2296   $270.23   $270.25   $270.20  
  Purchase #7 $154.38   5.655%   $163.1102   $163.11   $163.10   $163.10  
  7 purchase totals = $1,177.83       $1,270.8347   $1,270.83   $1,270.85   $1,270.80