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 $237.35   10.406%   $262.0486   $262.05   $262.05   $262.00  
  Purchase #2 $244.26   7.642%   $262.9263   $262.93   $262.95   $262.90  
  Purchase #3 $79.65   10.383%   $87.9201   $87.92   $87.90   $87.90  
  Purchase #4 $212.87   4.650%   $222.7685   $222.77   $222.75   $222.80  
  Purchase #5 $89.89   13.579%   $102.0962   $102.10   $102.10   $102.10  
  Purchase #6 $58.26   4.543%   $60.9068   $60.91   $60.90   $60.90  
  Purchase #7 $190.94   9.446%   $208.9762   $208.98   $209.00   $209.00  
  7 purchase totals = $1,113.22       $1,207.6427   $1,207.66   $1,207.65   $1,207.60