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 $88.32   5.788%   $93.432   $93.43   $93.45   $93.40  
  Purchase #2 $210.42   7.592%   $226.3951   $226.40   $226.40   $226.40  
  Purchase #3 $65.73   4.309%   $68.5623   $68.56   $68.55   $68.60  
  Purchase #4 $130.76   6.640%   $139.4425   $139.44   $139.45   $139.40  
  Purchase #5 $196.31   4.296%   $204.7435   $204.74   $204.75   $204.70  
  Purchase #6 $174.62   13.485%   $198.1675   $198.17   $198.15   $198.20  
  Purchase #7 $198.88   3.389%   $205.62   $205.62   $205.60   $205.60  
  7 purchase totals = $1,065.04       $1,136.3629   $1,136.36   $1,136.35   $1,136.30