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 $204.77   5.467%   $215.9648   $215.96   $215.95   $216.00  
  Purchase #2 $11.55   6.121%   $12.257   $12.26   $12.25   $12.30  
  Purchase #3 $73.51   11.638%   $82.0651   $82.07   $82.05   $82.10  
  Purchase #4 $54.79   6.545%   $58.376   $58.38   $58.40   $58.40  
  Purchase #5 $175.45   3.554%   $181.6855   $181.69   $181.70   $181.70  
  Purchase #6 $69.60   10.773%   $77.098   $77.10   $77.10   $77.10  
  Purchase #7 $125.91   3.134%   $129.856   $129.86   $129.85   $129.90  
  7 purchase totals = $715.58       $757.3024   $757.32   $757.30   $757.50