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 $69.27   5.764%   $73.2627   $73.26   $73.25   $73.30  
  Purchase #2 $241.73   4.632%   $252.9269   $252.93   $252.95   $252.90  
  Purchase #3 $125.86   8.395%   $136.4259   $136.43   $136.45   $136.40  
  Purchase #4 $133.91   9.270%   $146.3235   $146.32   $146.30   $146.30  
  Purchase #5 $220.77   5.589%   $233.1088   $233.11   $233.10   $233.10  
  Purchase #6 $11.77   9.861%   $12.9306   $12.93   $12.95   $12.90  
  Purchase #7 $191.36   4.554%   $200.0745   $200.07   $200.05   $200.10  
  7 purchase totals = $994.67       $1,055.0529   $1,055.05   $1,055.05   $1,055.00