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 $237.37   10.776%   $262.949   $262.95   $262.95   $262.90  
  Purchase #2 $32.56   11.190%   $36.2035   $36.20   $36.20   $36.20  
  Purchase #3 $49.46   9.613%   $54.2146   $54.21   $54.20   $54.20  
  Purchase #4 $105.48   4.362%   $110.081   $110.08   $110.10   $110.10  
  Purchase #5 $226.79   4.579%   $237.1747   $237.17   $237.15   $237.20  
  Purchase #6 $10.25   12.785%   $11.5605   $11.56   $11.55   $11.60  
  Purchase #7 $19.66   7.264%   $21.0881   $21.09   $21.10   $21.10  
  7 purchase totals = $681.57       $733.2714   $733.26   $733.25   $733.30