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 $118.87   6.327%   $126.3909   $126.39   $126.40   $126.40  
  Purchase #2 $29.36   4.771%   $30.7608   $30.76   $30.75   $30.80  
  Purchase #3 $77.51   5.274%   $81.5979   $81.60   $81.60   $81.60  
  Purchase #4 $48.31   6.281%   $51.3444   $51.34   $51.35   $51.30  
  Purchase #5 $43.57   6.639%   $46.4626   $46.46   $46.45   $46.50  
  Purchase #6 $169.93   8.708%   $184.7275   $184.73   $184.75   $184.70  
  Purchase #7 $215.59   8.383%   $233.6629   $233.66   $233.65   $233.70  
  7 purchase totals = $703.14       $754.9470   $754.94   $754.95   $755.00