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 $91.76   4.292%   $95.6983   $95.70   $95.70   $95.70  
  Purchase #2 $136.71   5.113%   $143.7   $143.70   $143.70   $143.70  
  Purchase #3 $117.34   9.284%   $128.2338   $128.23   $128.25   $128.20  
  Purchase #4 $89.72   10.487%   $99.1289   $99.13   $99.15   $99.10  
  Purchase #5 $95.51   8.158%   $103.3017   $103.30   $103.30   $103.30  
  Purchase #6 $154.58   7.473%   $166.1318   $166.13   $166.15   $166.10  
  Purchase #7 $212.36   12.578%   $239.0706   $239.07   $239.05   $239.10  
  7 purchase totals = $897.98       $975.2651   $975.26   $975.30   $975.20