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 $87.86   8.137%   $95.0092   $95.01   $95.00   $95.00  
  Purchase #2 $153.55   10.711%   $169.9967   $170.00   $170.00   $170.00  
  Purchase #3 $125.73   12.141%   $140.9949   $140.99   $141.00   $141.00  
  Purchase #4 $95.25   11.182%   $105.9009   $105.90   $105.90   $105.90  
  Purchase #5 $56.92   6.242%   $60.4729   $60.47   $60.45   $60.50  
  Purchase #6 $196.68   12.868%   $221.9888   $221.99   $222.00   $222.00  
  Purchase #7 $125.66   7.380%   $134.9337   $134.93   $134.95   $134.90  
  7 purchase totals = $841.65       $929.2971   $929.29   $929.30   $929.30