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 $187.56   11.439%   $209.015   $209.02   $209.00   $209.00  
  Purchase #2 $85.81   13.613%   $97.4913   $97.49   $97.50   $97.50  
  Purchase #3 $168.77   4.285%   $176.0018   $176.00   $176.00   $176.00  
  Purchase #4 $240.50   7.144%   $257.6813   $257.68   $257.70   $257.70  
  Purchase #5 $24.69   12.334%   $27.7353   $27.74   $27.75   $27.70  
  Purchase #6 $54.72   6.636%   $58.3512   $58.35   $58.35   $58.40  
  Purchase #7 $223.87   8.201%   $242.2296   $242.23   $242.25   $242.20  
  7 purchase totals = $985.92       $1,068.5055   $1,068.51   $1,068.55   $1,068.50