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 $179.31   12.763%   $202.1953   $202.20   $202.20   $202.20  
  Purchase #2 $157.66   5.649%   $166.5662   $166.57   $166.55   $166.60  
  Purchase #3 $214.25   10.603%   $236.9669   $236.97   $236.95   $237.00  
  Purchase #4 $240.81   8.708%   $261.7797   $261.78   $261.80   $261.80  
  Purchase #5 $161.36   5.451%   $170.1557   $170.16   $170.15   $170.20  
  Purchase #6 $182.74   12.645%   $205.8475   $205.85   $205.85   $205.80  
  Purchase #7 $200.74   8.433%   $217.6684   $217.67   $217.65   $217.70  
  7 purchase totals = $1,336.87       $1,461.1797   $1,461.20   $1,461.15   $1,461.30