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 $163.54   7.617%   $175.9968   $176.00   $176.00   $176.00  
  Purchase #2 $10.81   11.816%   $12.0873   $12.09   $12.10   $12.10  
  Purchase #3 $235.78   12.371%   $264.9483   $264.95   $264.95   $264.90  
  Purchase #4 $69.48   3.330%   $71.7937   $71.79   $71.80   $71.80  
  Purchase #5 $106.69   3.174%   $110.0763   $110.08   $110.10   $110.10  
  Purchase #6 $248.71   8.664%   $270.2582   $270.26   $270.25   $270.30  
  Purchase #7 $177.26   13.264%   $200.7718   $200.77   $200.75   $200.80  
  7 purchase totals = $1,012.27       $1,105.9324   $1,105.94   $1,105.95   $1,106.00