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 $23.31   13.246%   $26.3976   $26.40   $26.40   $26.40  
  Purchase #2 $228.29   13.582%   $259.2963   $259.30   $259.30   $259.30  
  Purchase #3 $99.93   12.740%   $112.6611   $112.66   $112.65   $112.70  
  Purchase #4 $113.72   10.682%   $125.8676   $125.87   $125.85   $125.90  
  Purchase #5 $205.68   4.348%   $214.623   $214.62   $214.60   $214.60  
  Purchase #6 $245.32   3.695%   $254.3846   $254.38   $254.40   $254.40  
  Purchase #7 $238.57   5.498%   $251.6866   $251.69   $251.70   $251.70  
  7 purchase totals = $1,154.82       $1,244.9168   $1,244.92   $1,244.90   $1,245.00