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 $72.33   8.691%   $78.6162   $78.62   $78.60   $78.60  
  Purchase #2 $119.91   13.706%   $136.3449   $136.34   $136.35   $136.30  
  Purchase #3 $113.80   13.589%   $129.2643   $129.26   $129.25   $129.30  
  Purchase #4 $206.52   10.285%   $227.7606   $227.76   $227.75   $227.80  
  Purchase #5 $196.72   8.632%   $213.7009   $213.70   $213.70   $213.70  
  Purchase #6 $198.78   9.822%   $218.3042   $218.30   $218.30   $218.30  
  Purchase #7 $21.29   3.392%   $22.0122   $22.01   $22.00   $22.00  
  7 purchase totals = $929.35       $1,026.0033   $1,025.99   $1,025.95   $1,026.00