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 $185.52   6.159%   $196.9462   $196.95   $196.95   $196.90  
  Purchase #2 $90.84   3.624%   $94.132   $94.13   $94.15   $94.10  
  Purchase #3 $140.67   8.533%   $152.6734   $152.67   $152.65   $152.70  
  Purchase #4 $26.37   7.358%   $28.3103   $28.31   $28.30   $28.30  
  Purchase #5 $226.25   8.764%   $246.0786   $246.08   $246.10   $246.10  
  Purchase #6 $201.72   12.715%   $227.3687   $227.37   $227.35   $227.40  
  Purchase #7 $230.69   13.563%   $261.9785   $261.98   $262.00   $262.00  
  7 purchase totals = $1,102.06       $1,207.4877   $1,207.49   $1,207.50   $1,207.50