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 $196.42   5.685%   $207.5865   $207.59   $207.60   $207.60  
  Purchase #2 $48.62   13.838%   $55.348   $55.35   $55.35   $55.30  
  Purchase #3 $104.65   12.195%   $117.4121   $117.41   $117.40   $117.40  
  Purchase #4 $10.36   5.637%   $10.944   $10.94   $10.95   $10.90  
  Purchase #5 $6.74   9.288%   $7.366   $7.37   $7.35   $7.40  
  Purchase #6 $142.47   12.403%   $160.1406   $160.14   $160.15   $160.10  
  Purchase #7 $148.95   12.658%   $167.8041   $167.80   $167.80   $167.80  
  7 purchase totals = $658.21       $726.6013   $726.60   $726.60   $726.50