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 $23.48   11.181%   $26.1053   $26.11   $26.10   $26.10  
  Purchase #2 $182.33   11.747%   $203.7483   $203.75   $203.75   $203.70  
  Purchase #3 $214.43   10.606%   $237.1724   $237.17   $237.15   $237.20  
  Purchase #4 $146.90   4.790%   $153.9365   $153.94   $153.95   $153.90  
  Purchase #5 $234.48   13.264%   $265.5814   $265.58   $265.60   $265.60  
  Purchase #6 $197.82   4.597%   $206.9138   $206.91   $206.90   $206.90  
  Purchase #7 $191.49   7.112%   $205.1088   $205.11   $205.10   $205.10  
  7 purchase totals = $1,190.93       $1,298.5665   $1,298.57   $1,298.55   $1,298.50