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 $58.32   7.457%   $62.6689   $62.67   $62.65   $62.70  
  Purchase #2 $171.54   12.611%   $193.1729   $193.17   $193.15   $193.20  
  Purchase #3 $167.76   12.252%   $188.314   $188.31   $188.30   $188.30  
  Purchase #4 $176.81   12.176%   $198.3384   $198.34   $198.35   $198.30  
  Purchase #5 $111.39   10.803%   $123.4235   $123.42   $123.40   $123.40  
  Purchase #6 $23.30   6.551%   $24.8264   $24.83   $24.85   $24.80  
  Purchase #7 $63.44   11.562%   $70.7749   $70.77   $70.75   $70.80  
  7 purchase totals = $772.56       $861.5190   $861.51   $861.45   $861.50