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 $246.55   6.552%   $262.704   $262.70   $262.70   $262.70  
  Purchase #2 $45.63   12.737%   $51.4419   $51.44   $51.45   $51.40  
  Purchase #3 $76.58   12.379%   $86.0598   $86.06   $86.05   $86.10  
  Purchase #4 $145.79   9.136%   $159.1094   $159.11   $159.10   $159.10  
  Purchase #5 $182.36   6.828%   $194.8115   $194.81   $194.80   $194.80  
  Purchase #6 $242.51   8.532%   $263.201   $263.20   $263.20   $263.20  
  Purchase #7 $124.35   10.328%   $137.1929   $137.19   $137.20   $137.20  
  7 purchase totals = $1,063.77       $1,154.5205   $1,154.51   $1,154.50   $1,154.50