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 $248.45   5.329%   $261.6899   $261.69   $261.70   $261.70  
  Purchase #2 $31.65   5.281%   $33.3214   $33.32   $33.30   $33.30  
  Purchase #3 $109.95   8.177%   $118.9406   $118.94   $118.95   $118.90  
  Purchase #4 $220.66   5.872%   $233.6172   $233.62   $233.60   $233.60  
  Purchase #5 $115.74   6.264%   $122.99   $122.99   $123.00   $123.00  
  Purchase #6 $181.45   8.869%   $197.5428   $197.54   $197.55   $197.50  
  Purchase #7 $151.35   4.559%   $158.25   $158.25   $158.25   $158.30  
  7 purchase totals = $1,059.25       $1,126.3519   $1,126.35   $1,126.35   $1,126.30