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 $213.57   10.346%   $235.666   $235.67   $235.65   $235.70  
  Purchase #2 $102.67   8.789%   $111.6937   $111.69   $111.70   $111.70  
  Purchase #3 $70.38   5.346%   $74.1425   $74.14   $74.15   $74.10  
  Purchase #4 $221.27   5.198%   $232.7716   $232.77   $232.75   $232.80  
  Purchase #5 $5.26   8.498%   $5.707   $5.71   $5.70   $5.70  
  Purchase #6 $249.25   7.529%   $268.016   $268.02   $268.00   $268.00  
  Purchase #7 $89.49   10.267%   $98.6779   $98.68   $98.70   $98.70  
  7 purchase totals = $951.89       $1,026.6747   $1,026.68   $1,026.65   $1,026.70