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 $114.29   10.602%   $126.407   $126.41   $126.40   $126.40  
  Purchase #2 $171.89   3.319%   $177.595   $177.60   $177.60   $177.60  
  Purchase #3 $161.69   12.166%   $181.3612   $181.36   $181.35   $181.40  
  Purchase #4 $124.65   5.578%   $131.603   $131.60   $131.60   $131.60  
  Purchase #5 $237.79   7.330%   $255.22   $255.22   $255.20   $255.20  
  Purchase #6 $46.59   5.188%   $49.0071   $49.01   $49.00   $49.00  
  Purchase #7 $36.96   8.154%   $39.9737   $39.97   $39.95   $40.00  
  7 purchase totals = $893.86       $961.1670   $961.17   $961.10   $961.20