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 $175.93   11.651%   $196.4276   $196.43   $196.45   $196.40  
  Purchase #2 $197.93   3.295%   $204.4518   $204.45   $204.45   $204.50  
  Purchase #3 $15.78   11.184%   $17.5448   $17.54   $17.55   $17.50  
  Purchase #4 $56.65   12.320%   $63.6293   $63.63   $63.65   $63.60  
  Purchase #5 $118.38   4.136%   $123.2762   $123.28   $123.30   $123.30  
  Purchase #6 $41.37   11.400%   $46.0862   $46.09   $46.10   $46.10  
  Purchase #7 $23.32   7.417%   $25.0496   $25.05   $25.05   $25.00  
  7 purchase totals = $629.36       $676.4655   $676.47   $676.55   $676.40