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 $88.33   7.249%   $94.733   $94.73   $94.75   $94.70  
  Purchase #2 $163.40   13.372%   $185.2498   $185.25   $185.25   $185.20  
  Purchase #3 $64.51   7.735%   $69.4998   $69.50   $69.50   $69.50  
  Purchase #4 $124.99   12.314%   $140.3813   $140.38   $140.40   $140.40  
  Purchase #5 $198.85   7.476%   $213.716   $213.72   $213.70   $213.70  
  Purchase #6 $203.56   4.762%   $213.2535   $213.25   $213.25   $213.30  
  Purchase #7 $98.57   11.452%   $109.8582   $109.86   $109.85   $109.90  
  7 purchase totals = $942.21       $1,026.6916   $1,026.69   $1,026.70   $1,026.70