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 $196.44   5.492%   $207.2285   $207.23   $207.25   $207.20  
  Purchase #2 $232.46   4.614%   $243.1857   $243.19   $243.20   $243.20  
  Purchase #3 $9.85   7.536%   $10.5923   $10.59   $10.60   $10.60  
  Purchase #4 $46.38   9.337%   $50.7105   $50.71   $50.70   $50.70  
  Purchase #5 $95.58   11.278%   $106.3595   $106.36   $106.35   $106.40  
  Purchase #6 $85.81   3.662%   $88.9524   $88.95   $88.95   $89.00  
  Purchase #7 $106.32   10.253%   $117.221   $117.22   $117.20   $117.20  
  7 purchase totals = $772.84       $824.2499   $824.25   $824.25   $824.30