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 $112.96   4.432%   $117.9664   $117.97   $117.95   $118.00  
  Purchase #2 $163.97   8.214%   $177.4385   $177.44   $177.45   $177.40  
  Purchase #3 $249.69   6.487%   $265.8874   $265.89   $265.90   $265.90  
  Purchase #4 $82.58   3.283%   $85.2911   $85.29   $85.30   $85.30  
  Purchase #5 $230.26   3.655%   $238.676   $238.68   $238.70   $238.70  
  Purchase #6 $187.86   9.593%   $205.8814   $205.88   $205.90   $205.90  
  Purchase #7 $97.26   5.423%   $102.5344   $102.53   $102.55   $102.50  
  7 purchase totals = $1,124.58       $1,193.6752   $1,193.68   $1,193.75   $1,193.70