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 $126.99   7.196%   $136.1282   $136.13   $136.15   $136.10  
  Purchase #2 $243.56   8.384%   $263.9801   $263.98   $264.00   $264.00  
  Purchase #3 $14.96   13.517%   $16.9821   $16.98   $17.00   $17.00  
  Purchase #4 $164.68   4.754%   $172.5089   $172.51   $172.50   $172.50  
  Purchase #5 $33.95   5.312%   $35.7534   $35.75   $35.75   $35.80  
  Purchase #6 $245.36   5.463%   $258.764   $258.76   $258.75   $258.80  
  Purchase #7 $39.39   6.139%   $41.8082   $41.81   $41.80   $41.80  
  7 purchase totals = $868.89       $925.9249   $925.92   $925.95   $926.00