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 $82.87   11.652%   $92.526   $92.53   $92.55   $92.50  
  Purchase #2 $62.56   6.173%   $66.4218   $66.42   $66.40   $66.40  
  Purchase #3 $152.97   10.581%   $169.1558   $169.16   $169.15   $169.20  
  Purchase #4 $185.63   4.120%   $193.278   $193.28   $193.30   $193.30  
  Purchase #5 $77.31   11.443%   $86.1566   $86.16   $86.15   $86.20  
  Purchase #6 $241.43   3.414%   $249.6724   $249.67   $249.65   $249.70  
  Purchase #7 $196.92   4.341%   $205.4683   $205.47   $205.45   $205.50  
  7 purchase totals = $999.69       $1,062.6789   $1,062.69   $1,062.65   $1,062.80