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 $119.41   5.709%   $126.2271   $126.23   $126.25   $126.20  
  Purchase #2 $233.27   6.275%   $247.9077   $247.91   $247.90   $247.90  
  Purchase #3 $156.87   12.467%   $176.427   $176.43   $176.45   $176.40  
  Purchase #4 $174.76   10.683%   $193.4296   $193.43   $193.45   $193.40  
  Purchase #5 $108.68   9.821%   $119.3535   $119.35   $119.35   $119.40  
  Purchase #6 $7.80   9.449%   $8.537   $8.54   $8.55   $8.50  
  Purchase #7 $164.92   9.845%   $181.1564   $181.16   $181.15   $181.20  
  7 purchase totals = $965.71       $1,053.0383   $1,053.05   $1,053.10   $1,053.00