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 $104.29   3.561%   $108.0038   $108.00   $108.00   $108.00  
  Purchase #2 $196.31   4.412%   $204.9712   $204.97   $204.95   $205.00  
  Purchase #3 $66.87   10.611%   $73.9656   $73.97   $73.95   $74.00  
  Purchase #4 $167.42   4.268%   $174.5655   $174.57   $174.55   $174.60  
  Purchase #5 $178.27   11.587%   $198.9261   $198.93   $198.95   $198.90  
  Purchase #6 $70.72   8.412%   $76.669   $76.67   $76.65   $76.70  
  Purchase #7 $170.51   8.723%   $185.3836   $185.38   $185.40   $185.40  
  7 purchase totals = $954.39       $1,022.4848   $1,022.49   $1,022.45   $1,022.60