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 $68.90   5.603%   $72.7605   $72.76   $72.75   $72.80  
  Purchase #2 $226.44   5.521%   $238.9418   $238.94   $238.95   $238.90  
  Purchase #3 $213.94   6.556%   $227.9659   $227.97   $227.95   $228.00  
  Purchase #4 $105.81   7.735%   $113.9944   $113.99   $114.00   $114.00  
  Purchase #5 $119.95   7.744%   $129.2389   $129.24   $129.25   $129.20  
  Purchase #6 $227.38   11.471%   $253.4628   $253.46   $253.45   $253.50  
  Purchase #7 $55.93   3.501%   $57.8881   $57.89   $57.90   $57.90  
  7 purchase totals = $1,018.35       $1,094.2524   $1,094.25   $1,094.25   $1,094.30