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 $204.80   10.750%   $226.816   $226.82   $226.80   $226.80  
  Purchase #2 $15.37   8.658%   $16.7007   $16.70   $16.70   $16.70  
  Purchase #3 $139.80   8.831%   $152.1457   $152.15   $152.15   $152.10  
  Purchase #4 $158.46   10.715%   $175.439   $175.44   $175.45   $175.40  
  Purchase #5 $239.44   11.606%   $267.2294   $267.23   $267.25   $267.20  
  Purchase #6 $31.39   7.319%   $33.6874   $33.69   $33.70   $33.70  
  Purchase #7 $244.68   6.796%   $261.3085   $261.31   $261.30   $261.30  
  7 purchase totals = $1,033.94       $1,133.3267   $1,133.34   $1,133.35   $1,133.20