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 $188.49   9.238%   $205.9027   $205.90   $205.90   $205.90  
  Purchase #2 $241.42   4.520%   $252.3322   $252.33   $252.35   $252.30  
  Purchase #3 $197.95   5.665%   $209.1639   $209.16   $209.15   $209.20  
  Purchase #4 $131.86   3.689%   $136.7243   $136.72   $136.70   $136.70  
  Purchase #5 $137.50   10.232%   $151.569   $151.57   $151.55   $151.60  
  Purchase #6 $43.26   4.548%   $45.2275   $45.23   $45.25   $45.20  
  Purchase #7 $113.79   4.139%   $118.4998   $118.50   $118.50   $118.50  
  7 purchase totals = $1,054.27       $1,119.4194   $1,119.41   $1,119.40   $1,119.40