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 $243.30   7.715%   $262.0706   $262.07   $262.05   $262.10  
  Purchase #2 $171.57   8.122%   $185.5049   $185.50   $185.50   $185.50  
  Purchase #3 $224.88   10.576%   $248.6633   $248.66   $248.65   $248.70  
  Purchase #4 $197.39   4.175%   $205.631   $205.63   $205.65   $205.60  
  Purchase #5 $176.29   10.320%   $194.4831   $194.48   $194.50   $194.50  
  Purchase #6 $23.96   10.588%   $26.4969   $26.50   $26.50   $26.50  
  Purchase #7 $23.59   11.593%   $26.3248   $26.32   $26.30   $26.30  
  7 purchase totals = $1,060.98       $1,149.1746   $1,149.16   $1,149.15   $1,149.20