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 $86.34   10.788%   $95.6544   $95.65   $95.65   $95.70  
  Purchase #2 $206.87   13.553%   $234.9071   $234.91   $234.90   $234.90  
  Purchase #3 $109.37   9.374%   $119.6223   $119.62   $119.60   $119.60  
  Purchase #4 $30.99   8.852%   $33.7332   $33.73   $33.75   $33.70  
  Purchase #5 $149.47   9.553%   $163.7489   $163.75   $163.75   $163.70  
  Purchase #6 $166.48   11.588%   $185.7717   $185.77   $185.75   $185.80  
  Purchase #7 $83.97   3.250%   $86.699   $86.70   $86.70   $86.70  
  7 purchase totals = $833.49       $920.1366   $920.13   $920.10   $920.10